diff --git a/include/boost/variant2/variant.hpp b/include/boost/variant2/variant.hpp
index 8f6a223..0155de9 100644
--- a/include/boost/variant2/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@@ -16,6 +16,7 @@
 #include <exception>
 #include <cassert>
 #include <initializer_list>
+#include <utility>
 
 //
 
@@ -353,7 +354,7 @@ template<class... T> struct variant_base_impl<mp_true, mp_true, T...>
     {
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> i ) noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> ) noexcept
     {
         size_t const J = I+1;
 
@@ -362,7 +363,7 @@ template<class... T> struct variant_base_impl<mp_true, mp_true, T...>
         return st1_.get( mp_size_t<J>() );
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> i ) const noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> ) const noexcept
     {
         size_t const J = I+1;
 
@@ -407,7 +408,7 @@ template<class... T> struct variant_base_impl<mp_true, mp_false, T...>
     {
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> i ) noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> ) noexcept
     {
         size_t const J = I+1;
 
@@ -417,7 +418,7 @@ template<class... T> struct variant_base_impl<mp_true, mp_false, T...>
         return ix_ >= 0? st1_.get( j ): st2_.get( j );
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> i ) const noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> ) const noexcept
     {
         size_t const J = I+1;
 
@@ -478,7 +479,7 @@ template<class... T> struct variant_base_impl<mp_false, mp_true, T...>
         _destroy();
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> i ) noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> ) noexcept
     {
         size_t const J = I+1;
 
@@ -487,7 +488,7 @@ template<class... T> struct variant_base_impl<mp_false, mp_true, T...>
         return st1_.get( mp_size_t<J>() );
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> i ) const noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> ) const noexcept
     {
         size_t const J = I+1;
 
@@ -563,7 +564,7 @@ template<class... T> struct variant_base_impl<mp_false, mp_false, T...>
         _destroy();
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> i ) noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I>& _get_impl( mp_size_t<I> ) noexcept
     {
         size_t const J = I+1;
 
@@ -573,7 +574,7 @@ template<class... T> struct variant_base_impl<mp_false, mp_false, T...>
         return ix_ >= 0? st1_.get( j ): st2_.get( j );
     }
 
-    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> i ) const noexcept
+    template<std::size_t I> constexpr mp_at_c<variant<T...>, I> const& _get_impl( mp_size_t<I> ) const noexcept
     {
         size_t const J = I+1;
 
@@ -638,6 +639,55 @@ template<std::size_t I> struct is_in_place_index<in_place_index_t<I>>: std::true
 
 } // namespace detail
 
+// is_nothrow_swappable
+
+namespace detail
+{
+
+namespace det2
+{
+
+using std::swap;
+
+template<class T> using is_swappable_impl = decltype(swap(std::declval<T&>(), std::declval<T&>()));
+
+#if BOOST_WORKAROUND( BOOST_MSVC, <= 1910 )
+
+template<class T> struct is_nothrow_swappable_impl_
+{
+    static constexpr bool value = noexcept(swap(std::declval<T&>(), std::declval<T&>()));
+};
+
+template<class T> using is_nothrow_swappable_impl = mp_bool< is_nothrow_swappable_impl_<T>::value >;
+
+#else
+
+template<class T> using is_nothrow_swappable_impl = std::enable_if_t<noexcept(swap(std::declval<T&>(), std::declval<T&>()))>;
+
+#endif
+
+} // namespace det2
+
+template<class T> struct is_swappable: mp_valid<det2::is_swappable_impl, T>
+{
+};
+
+#if BOOST_WORKAROUND( BOOST_MSVC, <= 1910 )
+
+template<class T> struct is_nothrow_swappable: mp_eval_if<mp_not<is_swappable<T>>, mp_false, det2::is_nothrow_swappable_impl, T>
+{
+};
+
+#else
+
+template<class T> struct is_nothrow_swappable: mp_valid<det2::is_nothrow_swappable_impl, T>
+{
+};
+
+#endif
+
+} // namespace detail
+
 // variant
 
 template<class... T> class variant: private variant2::detail::variant_base<T...>
@@ -715,7 +765,7 @@ public:
     {
         mp_for_each<mp_iota_c<sizeof...(T)>>([&]( auto I ){
 
-            constexpr auto J = decltype(I)::value;
+            constexpr auto J = I.value;
 
             if( J == r.index() )
             {
@@ -738,7 +788,7 @@ public:
     {
         mp_for_each<mp_iota_c<sizeof...(T)>>([&]( auto I ){
 
-            constexpr auto J = decltype(I)::type::value;
+            constexpr auto J = I.value;
 
             if( J == r.index() )
             {
@@ -805,7 +855,29 @@ public:
 
     // swap
 
-    void swap( variant& r ); // noexcept( ... )
+    void swap( variant& r ) noexcept( mp_all<std::is_nothrow_move_constructible<T>..., variant2::detail::is_nothrow_swappable<T>...>::value )
+    {
+        if( index() == r.index() )
+        {
+            mp_for_each<mp_iota_c<sizeof...(T)>>([&]( auto I ){
+
+                constexpr auto J = I.value;
+
+                if( J == this->index() )
+                {
+                    using std::swap;
+                    swap( get<J>(*this), get<J>(r) );
+                }
+
+            });
+        }
+        else
+        {
+            variant tmp( std::move(*this) );
+            *this = std::move( r );
+            r = std::move( tmp );
+        }
+    }
 
     // private accessors
 
@@ -916,7 +988,10 @@ template<class... T> constexpr bool operator>=( variant<T...> const & v, variant
 template<class Visitor, class... Variants> constexpr void visit( Visitor&&, Variants&&... );
 
 // specialized algorithms
-template<class... T> void swap( variant<T...> & v, variant<T...> & w ); // noexcept(see below );
+template<class... T> void swap( variant<T...> & v, variant<T...> & w ) noexcept( noexcept(v.swap(w)) )
+{
+    v.swap( w );
+}
 
 } // namespace variant2
 } // namespace boost
diff --git a/test/Jamfile b/test/Jamfile
index 07e9465..1670e6a 100644
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -34,3 +34,4 @@ run variant_move_assign.cpp : : : $(REQ) ;
 run variant_value_assign.cpp : : : $(REQ) ;
 run variant_emplace_index.cpp : : : $(REQ) ;
 run variant_emplace_type.cpp : : : $(REQ) ;
+run variant_swap.cpp : : : $(REQ) ;
diff --git a/test/variant_swap.cpp b/test/variant_swap.cpp
new file mode 100644
index 0000000..679f5f8
--- /dev/null
+++ b/test/variant_swap.cpp
@@ -0,0 +1,259 @@
+
+// Copyright 2017 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+#include <utility>
+#include <string>
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X1
+{
+    int v;
+
+    X1(): v(0) {}
+    explicit X1(int v): v(v) {}
+    X1(X1 const& r): v(r.v) {}
+    X1(X1&& r): v(r.v) {}
+    X1& operator=( X1 const& r ) { v = r.v; return *this; }
+    X1& operator=( X1&& r ) { v = r.v; return *this; }
+};
+
+inline bool operator==( X1 const& a, X1 const& b ) { return a.v == b.v; }
+
+STATIC_ASSERT( !std::is_nothrow_default_constructible<X1>::value );
+STATIC_ASSERT( !std::is_nothrow_copy_constructible<X1>::value );
+STATIC_ASSERT( !std::is_nothrow_move_constructible<X1>::value );
+STATIC_ASSERT( !std::is_nothrow_copy_assignable<X1>::value );
+STATIC_ASSERT( !std::is_nothrow_move_assignable<X1>::value );
+
+struct X2
+{
+    int v;
+
+    X2(): v(0) {}
+    explicit X2(int v): v(v) {}
+    X2(X2 const& r): v(r.v) {}
+    X2(X2&& r): v(r.v) {}
+    X2& operator=( X2 const& r ) { v = r.v; return *this; }
+    X2& operator=( X2&& r ) { v = r.v; return *this; }
+};
+
+inline bool operator==( X2 const& a, X2 const& b ) { return a.v == b.v; }
+
+STATIC_ASSERT( !std::is_nothrow_default_constructible<X2>::value );
+STATIC_ASSERT( !std::is_nothrow_copy_constructible<X2>::value );
+STATIC_ASSERT( !std::is_nothrow_move_constructible<X2>::value );
+STATIC_ASSERT( !std::is_nothrow_copy_assignable<X2>::value );
+STATIC_ASSERT( !std::is_nothrow_move_assignable<X2>::value );
+
+int main()
+{
+    {
+        variant<int> v;
+        BOOST_TEST_EQ( get<0>(v), 0 );
+
+        variant<int> v2( 1 );
+        BOOST_TEST_EQ( get<0>(v2), 1 );
+
+        swap( v, v2 );
+        BOOST_TEST_EQ( get<0>(v), 1 );
+        BOOST_TEST_EQ( get<0>(v2), 0 );
+
+        variant<int> v3( 2 );
+        BOOST_TEST_EQ( get<0>(v3), 2 );
+
+        swap( v, v3 );
+        BOOST_TEST_EQ( get<0>(v), 2 );
+        BOOST_TEST_EQ( get<0>(v3), 1 );
+    }
+
+    {
+        variant<int, float> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 0 );
+
+        variant<int, float> v2( 1 );
+
+        BOOST_TEST_EQ( v2.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v2), 1 );
+
+        swap( v, v2 );
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 1 );
+
+        BOOST_TEST_EQ( v2.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v2), 0 );
+
+        variant<int, float> v3( 3.14f );
+
+        BOOST_TEST_EQ( v3.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v3), 3.14f );
+
+        swap( v, v3 );
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v), 3.14f );
+
+        BOOST_TEST_EQ( v3.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v3), 1 );
+
+        variant<int, float> v4( 3.15f );
+
+        BOOST_TEST_EQ( v4.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v4), 3.15f );
+
+        swap( v, v4 );
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v), 3.15f );
+
+        BOOST_TEST_EQ( v4.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v4), 3.14f );
+    }
+
+    {
+        variant<int, int, float, std::string> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), 0 );
+
+        variant<int, int, float, std::string> v2( in_place_index<1>, 1 );
+
+        BOOST_TEST_EQ( v2.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v2), 1 );
+
+        swap( v, v2 );
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v), 1 );
+
+        BOOST_TEST_EQ( v2.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v2), 0 );
+
+        variant<int, int, float, std::string> v3( 3.14f );
+
+        BOOST_TEST_EQ( v3.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v3), 3.14f );
+
+        swap( v, v3 );
+
+        BOOST_TEST_EQ( v.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v), 3.14f );
+
+        BOOST_TEST_EQ( v3.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v3), 1 );
+
+        variant<int, int, float, std::string> v4( 3.15f );
+
+        BOOST_TEST_EQ( v4.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v4), 3.15f );
+
+        swap( v, v4 );
+
+        BOOST_TEST_EQ( v.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v), 3.15f );
+
+        BOOST_TEST_EQ( v4.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v4), 3.14f );
+
+        variant<int, int, float, std::string> v5( "s1" );
+
+        BOOST_TEST_EQ( v5.index(), 3 );
+        BOOST_TEST_EQ( get<3>(v5), std::string("s1") );
+
+        swap( v, v5 );
+
+        BOOST_TEST_EQ( v.index(), 3 );
+        BOOST_TEST_EQ( get<3>(v), std::string("s1") );
+
+        BOOST_TEST_EQ( v5.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v5), 3.15f );
+
+        variant<int, int, float, std::string> v6( "s2" );
+
+        BOOST_TEST_EQ( v6.index(), 3 );
+        BOOST_TEST_EQ( get<3>(v6), std::string("s2") );
+
+        swap( v, v6 );
+
+        BOOST_TEST_EQ( v.index(), 3 );
+        BOOST_TEST_EQ( get<3>(v), std::string("s2") );
+
+        BOOST_TEST_EQ( v6.index(), 3 );
+        BOOST_TEST_EQ( get<3>(v6), std::string("s1") );
+    }
+
+    {
+        variant<X1, X2> v;
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 0 );
+
+        variant<X1, X2> v2( X1{1} );
+
+        BOOST_TEST_EQ( v2.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v2).v, 1 );
+
+        swap( v, v2 );
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+
+        BOOST_TEST_EQ( v2.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v2).v, 0 );
+
+        variant<X1, X2> v3( in_place_index<1>, 2 );
+
+        BOOST_TEST_EQ( v3.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v3).v, 2 );
+
+        swap( v, v3 );
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+
+        BOOST_TEST_EQ( v3.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v3).v, 1 );
+
+        variant<X1, X2> v4( in_place_index<1>, 3 );
+
+        BOOST_TEST_EQ( v4.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v4).v, 3 );
+
+        swap( v, v4 );
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 3 );
+
+        BOOST_TEST_EQ( v4.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v4).v, 2 );
+
+        variant<X1, X2> v5( in_place_index<0>, 4 );
+
+        BOOST_TEST_EQ( v5.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v5).v, 4 );
+
+        swap( v, v5 );
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 4 );
+
+        BOOST_TEST_EQ( v5.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v5).v, 3 );
+    }
+
+    return boost::report_errors();
+}