diff --git a/aclocal.m4 b/aclocal.m4
index 0c4c8bf29..43b6b221f 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -524,3 +524,43 @@ fi
 ])
 
 #-----------------------------------------------------------------------------#
+#
+# Check if the POSIX threads library is pthreads-win32.
+#
+
+AC_DEFUN([MERCURY_HAVE_PTHREADS_WIN32], [
+
+AC_MSG_CHECKING([if we are using pthreads-win32])
+
+cat > conftest.c << EOF
+
+#include <pthread.h>
+#include <stdio.h>
+
+int main(int argc, char **argv)
+{
+
+#if defined(PTW32_VERSION)
+    return 0;
+#else
+    return 1;
+#endif
+
+}
+
+EOF
+
+echo "$CC -o conftest contest.c" >&AC_FD_CC 2>&1
+if
+    $CC -o conftest conftest.c
+then
+    mercury_cv_have_pthreads_win32="yes"
+else
+    mercury_cv_have_pthreads_win32="no"
+fi
+
+AC_MSG_RESULT($mercury_cv_have_pthreads_win32)
+
+])
+
+#-----------------------------------------------------------------------------#
diff --git a/configure.in b/configure.in
index 70b789e52..413ba6b2f 100644
--- a/configure.in
+++ b/configure.in
@@ -59,6 +59,7 @@ AC_PREREQ(2.58)
 # Strip out any site or system specific configuration files since their
 # presence when reconfiguring will result in the command line used to invoke
 # configure being invalid.
+	
 # Also quote any args containing shell metacharacters.
 #
 # NOTE: Some macros, e.g. AC_CHECK_PROG, overwrite the argument list,
@@ -1222,6 +1223,19 @@ if test "$MR_HAVE_UCONTEXT_H" != 1; then
     MERCURY_CHECK_FOR_HEADERS(sys/ucontext.h)
 fi
 
+if test "$MR_HAVE_PTHREAD_H" = 1
+then
+    case "$host" in
+        *mingw*)
+            MERCURY_HAVE_PTHREADS_WIN32
+            if test $mercury_cv_have_pthreads_win32 = "yes"
+            then
+                AC_DEFINE([MR_PTHREADS_WIN32])
+            fi 
+        ;;
+    esac
+fi
+
 #-----------------------------------------------------------------------------#
 #
 # Check whether we can set the FP rounding mode
diff --git a/runtime/mercury_conf.h.in b/runtime/mercury_conf.h.in
index 723697f30..816d61cc9 100644
--- a/runtime/mercury_conf.h.in
+++ b/runtime/mercury_conf.h.in
@@ -409,9 +409,12 @@
 ** MR_THREAD_LOCAL_STORAGE is defined if the thread-local storage extension
 ** is supported.  That is, the compiler extends the C language with the
 ** `__thread' specifier.
+**
+** MR_PTHREADS_WIN32 is defined if we are using the pthreads-win32 library.
 */
 #undef MR_DIGITAL_UNIX_PTHREADS
 #undef MR_THREAD_LOCAL_STORAGE
+#undef MR_PTHREADS_WIN32
 
 /*
 ** The bytecode files represent floats in 64-bit IEEE format.