diff --git a/msvc/Makefile b/msvc/Makefile
index 5626f4ebe..5ca37e886 100755
--- a/msvc/Makefile
+++ b/msvc/Makefile
@@ -35,7 +35,10 @@ ECL_THREADS   = 1
 ECL_UNICODE   =
 
 # Set it to non-empty to enable Win32 debug support
-#ECL_DEBUG   = 1
+#ECL_DEBUG = 1
+
+# Set it to non-empty to support SSE2 intrinsics
+ECL_SSE =
 
 # Add the extensions to include in the build process. Comment any
 # of the following lines to remove a feature from the build process
@@ -75,18 +78,22 @@ MKNSI   = makensis.exe
 
 # ==================== Flags ====================
 
+!if "$(ECL_SSE)" != ""
+CFLAGS_SSE=/arch:SSE2
+!endif
+
 #
 # Configuration-specific (Debug/Release) options
 #
 !if "$(ECL_DEBUG)" != ""
 CFLAGS_OPTIMIZE = /Od
-CFLAGS_CONFIG = /Zi /D_DEBUG /MDd $(CFLAGS_OPTIMIZE)
+CFLAGS_CONFIG = /Zi /D_DEBUG /MDd $(CFLAGS_OPTIMIZE) $(CFLAGS_SSE)
 LDFLAGS_CONFIG = /debug /nodefaultlib:msvcrt.lib
 SHARED_LDFLAGS = /LDd
 GCFLAGS =
 !else
 CFLAGS_OPTIMIZE = /O2
-CFLAGS_CONFIG = /DNDEBUG /MD $(CFLAGS_OPTIMIZE)
+CFLAGS_CONFIG = /DNDEBUG /MD $(CFLAGS_OPTIMIZE) $(CFLAGS_SSE)
 LDFLAGS_CONFIG = /nodefaultlib:msvcrtd.lib
 SHARED_LDFLAGS = /LD
 GCFLAGS = nodebug=1
@@ -312,7 +319,7 @@ eclmin.lib: eclgmp.lib eclgc.lib lsp/config.lsp
 	cd c
 	$(MAKE) ECL_VERSION_NUMBER=$(ECL_VERSION_NUMBER) \
 	        ECL_THREADS=$(ECL_THREADS) ECL_UNICODE=$(ECL_UNICODE) \
-		"ECL_CFLAGS=$(CFLAGS) -DGC_BUILD"
+		ECL_SSE=$(ECL_SSE) "ECL_CFLAGS=$(CFLAGS) -DGC_BUILD"
 	cd ..
 eclgc.lib:
 	cd gc
diff --git a/msvc/c/Makefile b/msvc/c/Makefile
index e771263bd..972f5d25c 100755
--- a/msvc/c/Makefile
+++ b/msvc/c/Makefile
@@ -18,6 +18,12 @@ ECL_UNICODE_FLAG=1
 ECL_UNICODE_FLAG=0
 !endif
 
+!if "$(ECL_SSE)" != ""
+ECL_SSE_FLAG=1
+!else
+ECL_SSE_FLAG=0
+!endif
+
 # Programs used by "make":
 #
 TRUE_CC = cl
@@ -107,6 +113,7 @@ $(DPP): $(srcdir)/dpp.c $(srcdir)/symbols_list2.h ../ecl/config.h
 		"@ECL_VERSION_NUMBER@" "$(ECL_VERSION_NUMBER)" \
 		"@ECL_THREADS@" "$(ECL_THREADS_FLAG)" \
 		"@ECL_UNICODE@" "$(ECL_UNICODE_FLAG)" \
+		"@ECL_SSE@" "$(ECL_SSE_FLAG)" \
 	        < ..\ecl\config.h.msvc6 > $@
 
 #
diff --git a/msvc/ecl/config.h.msvc6 b/msvc/ecl/config.h.msvc6
index fc459c5de..64a1ea5a7 100755
--- a/msvc/ecl/config.h.msvc6
+++ b/msvc/ecl/config.h.msvc6
@@ -223,6 +223,14 @@ typedef unsigned int uint32_t;
 #define ecl_unlikely(form) (form)
 #define ecl_attr_noreturn
 
+#if defined(__SSE2__) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2)
+#define ECL_SSE2 @ECL_SSE2@
+#if !ECL_SSE2
+#undef ECL_SSE2
+#endif
+#endif
+
+
 /* -CUT-: Everything below this mark will not be installed		*/
 /* -------------------------------------------------------------------- *
  *	BUILD OPTIONS WHICH NEED NOT BE EXPORTED			*
diff --git a/src/aclocal.m4 b/src/aclocal.m4
index 2c7195bf5..bc4216118 100644
--- a/src/aclocal.m4
+++ b/src/aclocal.m4
@@ -770,6 +770,39 @@ esac
 AC_SUBST(ECL_FPE_CODE)
 ])
 
+dnl ----------------------------------------------------------------------
+dnl Decide whether ECL should export SSE intrinsics
+dnl
+AC_DEFUN([ECL_SSE],[
+if test "x$with_sse" = xyes; then
+ AC_MSG_CHECKING([for SSE intrinsics])
+ AC_TRY_LINK([
+#include <xmmintrin.h>
+#include <emmintrin.h>
+],[__m128 value;
+_mm_getcsr();],[sse_included=yes],[sse_included=no])
+ if test "$sse_included" = "no"; then
+  OLD_CFLAGS="$CFLAGS"
+  CFLAGS="$CFLAGS -msse2"
+  AC_TRY_LINK([
+#include <xmmintrin.h>
+#include <emmintrin.h>
+],[__m128 value;
+_mm_getcsr();],[sse_included=yes],[sse_included=no])
+  if test "$sse_included" = "no"; then
+   CFLAGS="$OLD_CFLAGS"
+   with_sse=no
+  fi
+ fi
+ if test "x$with_sse" = xyes; then
+  AC_DEFINE(ECL_SSE2)
+  AC_MSG_RESULT([yes])
+ else
+  AC_MSG_RESULT([no])
+ fi
+fi
+])
+
 dnl ----------------------------------------------------------------------
 dnl Check whether we have unnamed POSIX semaphores available
 AC_DEFUN([ECL_POSIX_SEMAPHORES],[
diff --git a/src/configure b/src/configure
index 46990c49a..22c543858 100755
--- a/src/configure
+++ b/src/configure
@@ -797,6 +797,7 @@ with_dffi
 with_fpe
 with_signed_zero
 with_ieee_fp
+with_sse
 enable_unicode
 enable_longdouble
 enable_c99complex
@@ -1520,6 +1521,9 @@ Optional Packages:
                           allow for IEEE signed zeros (default=YES).
   --with-ieee-fp={yes|no} full IEEE floating point system, including denormals
                           (default=YES). Implies signed-zero and fpe
+  --with-sse={yes|no|auto}
+                          implement SSE intrinsics in ECL (default=NO). Only
+                          works when supported by the compiler
   --with-debug-cflags     add debug flags to the compiler invocation
                           (yes,no,actual flags,default=YES)
   --with-profile-cflags   add profiling flags to the compiler invocation
@@ -2303,6 +2307,15 @@ else
 fi
 
 
+
+# Check whether --with-sse was given.
+if test "${with_sse+set}" = set; then
+  withval=$with_sse;
+else
+  with_sse="no"
+fi
+
+
 # Check whether --enable-unicode was given.
 if test "${enable_unicode+set}" = set; then
   enableval=$enable_unicode;
@@ -10434,6 +10447,133 @@ esac
 
 
 
+if test "x$with_sse" = xyes; then
+ { $as_echo "$as_me:$LINENO: checking for SSE intrinsics" >&5
+$as_echo_n "checking for SSE intrinsics... " >&6; }
+ cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+#include <xmmintrin.h>
+#include <emmintrin.h>
+
+int
+main ()
+{
+__m128 value;
+_mm_getcsr();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
+$as_echo "$ac_try_echo") >&5
+  (eval "$ac_link") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && {
+	 test -z "$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext && {
+	 test "$cross_compiling" = yes ||
+	 $as_test_x conftest$ac_exeext
+       }; then
+  sse_included=yes
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	sse_included=no
+fi
+
+rm -rf conftest.dSYM
+rm -f core conftest.err conftest.$ac_objext conftest_ipa8_conftest.oo \
+      conftest$ac_exeext conftest.$ac_ext
+ if test "$sse_included" = "no"; then
+  OLD_CFLAGS="$CFLAGS"
+  CFLAGS="$CFLAGS -msse2"
+  cat >conftest.$ac_ext <<_ACEOF
+/* confdefs.h.  */
+_ACEOF
+cat confdefs.h >>conftest.$ac_ext
+cat >>conftest.$ac_ext <<_ACEOF
+/* end confdefs.h.  */
+
+#include <xmmintrin.h>
+#include <emmintrin.h>
+
+int
+main ()
+{
+__m128 value;
+_mm_getcsr();
+  ;
+  return 0;
+}
+_ACEOF
+rm -f conftest.$ac_objext conftest$ac_exeext
+if { (ac_try="$ac_link"
+case "(($ac_try" in
+  *\"* | *\`* | *\\*) ac_try_echo=\$ac_try;;
+  *) ac_try_echo=$ac_try;;
+esac
+eval ac_try_echo="\"\$as_me:$LINENO: $ac_try_echo\""
+$as_echo "$ac_try_echo") >&5
+  (eval "$ac_link") 2>conftest.er1
+  ac_status=$?
+  grep -v '^ *+' conftest.er1 >conftest.err
+  rm -f conftest.er1
+  cat conftest.err >&5
+  $as_echo "$as_me:$LINENO: \$? = $ac_status" >&5
+  (exit $ac_status); } && {
+	 test -z "$ac_c_werror_flag" ||
+	 test ! -s conftest.err
+       } && test -s conftest$ac_exeext && {
+	 test "$cross_compiling" = yes ||
+	 $as_test_x conftest$ac_exeext
+       }; then
+  sse_included=yes
+else
+  $as_echo "$as_me: failed program was:" >&5
+sed 's/^/| /' conftest.$ac_ext >&5
+
+	sse_included=no
+fi
+
+rm -rf conftest.dSYM
+rm -f core conftest.err conftest.$ac_objext conftest_ipa8_conftest.oo \
+      conftest$ac_exeext conftest.$ac_ext
+  if test "$sse_included" = "no"; then
+   CFLAGS="$OLD_CFLAGS"
+   with_sse=no
+  fi
+ fi
+ if test "x$with_sse" = xyes; then
+  cat >>confdefs.h <<\_ACEOF
+#define ECL_SSE2 1
+_ACEOF
+
+  { $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+ else
+  { $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+ fi
+fi
+
+
 if test "$enable_longdouble" != "no" ; then
 { $as_echo "$as_me:$LINENO: checking for long double" >&5
 $as_echo_n "checking for long double... " >&6; }
diff --git a/src/configure.in b/src/configure.in
index b1564fd5b..f84930bd5 100644
--- a/src/configure.in
+++ b/src/configure.in
@@ -199,6 +199,12 @@ AC_ARG_WITH(ieee-fp,
                   [Implies signed-zero and fpe]),
   [], [with_ieee_fp="yes"])
 
+AC_ARG_WITH(sse,
+  AS_HELP_STRING( [--with-sse={yes|no|auto}],
+                  [implement SSE intrinsics in ECL (default=NO).]
+                  [Only works when supported by the compiler]),
+  [], [with_sse="no"])
+
 AC_ARG_ENABLE(unicode,
   AS_HELP_STRING( [--enable-unicode],
                   [enable support for unicode (default=NO)]),
@@ -658,6 +664,7 @@ if test "x$with_dffi" != "xno"; then
 ECL_FFI
 fi
 ECL_FPE_MODEL
+ECL_SSE
 
 if test "$enable_longdouble" != "no" ; then
 AC_CHECK_TYPES([long double])
diff --git a/src/h/config.h.in b/src/h/config.h.in
index b0bb279e7..8261663d5 100644
--- a/src/h/config.h.in
+++ b/src/h/config.h.in
@@ -254,7 +254,7 @@ typedef unsigned @CL_FIXNUM_TYPE@ cl_hashkey;
 #endif
 
 #if defined(__SSE2__) || (defined(_M_IX86_FP) && _M_IX86_FP >= 2)
-#define ECL_SSE2
+#undef ECL_SSE2
 #endif
 
 /* -CUT-: Everything below this mark will not be installed		*/