diff --git a/lib/isc/win32/include/isc/once.h b/lib/isc/win32/include/isc/once.h
new file mode 100644
index 0000000000..f0ec235806
--- /dev/null
+++ b/lib/isc/win32/include/isc/once.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 1999  Internet Software Consortium.
+ * 
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+/* $Id: once.h,v 1.1 1999/09/23 18:14:16 tale Exp $ */
+
+#ifndef ISC_ONCE_H
+#define ISC_ONCE_H 1
+
+#include <isc/lang.h>
+#include <isc/result.h>
+
+ISC_LANG_BEGINDECLS
+
+typedef struct {
+	int status;
+#ifndef ISC_ONCE_USE_MUTEX
+	int counter;
+#endif
+} isc_once_t;
+
+#define ISC_ONCE_INIT_NEEDED 0
+#define ISC_ONCE_INIT_DONE 1
+
+#ifdef ISC_ONCE_USE_MUTEX
+#define ISC_ONCE_INIT { ISC_ONCE_INIT_NEEDED }
+#else
+#define ISC_ONCE_INIT { ISC_ONCE_INIT_NEEDED, 1 }
+#endif
+
+isc_result_t
+isc_once_do(isc_once_t *controller, void(*function)(void));
+
+ISC_LANG_ENDDECLS
+
+#endif /* ISC_ONCE_H */
diff --git a/lib/isc/win32/once.c b/lib/isc/win32/once.c
new file mode 100644
index 0000000000..a5ff365d44
--- /dev/null
+++ b/lib/isc/win32/once.c
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 1999  Internet Software Consortium.
+ * 
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
+ * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
+ * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+ * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+ * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+ * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
+ * SOFTWARE.
+ */
+
+/* $Id: once.c,v 1.1 1999/09/23 18:14:16 tale Exp $ */
+
+/* Principal Authors: DCL */
+
+#ifdef ISC_ONCE_USE_MUTEX
+#include <stdio.h>
+#include <process.h>
+#endif
+
+#include <windows.h>
+
+#include <isc/once.h>
+#include <isc/assertions.h>
+
+#ifdef ISC_ONCE_USE_MUTEX
+
+/*
+ * XXXDCL someone (me? bob?) should decide which method to use,
+ * the mutex method or the InterlockedDecrement method.
+ */
+
+isc_result_t
+isc_once_do(isc_once_t *controller, void(*function)(void))
+
+{
+	char mutex_name[64];
+	HANDLE mutex;
+
+	REQUIRE(controller != NULL && function != NULL);
+
+	if (controller->status == ISC_ONCE_INIT_NEEDED) {	
+	
+		/*
+		 * Create a name that is associated only with this process
+		 * and controller.
+		 */
+		sprintf(mutex_name, "__isc_once_do_%ld:%p",
+			getpid(), controller);
+
+		/*
+		 * Create the mutex (or attach to the existing mutex)
+		 * and lock it. 
+		 */
+		mutex = CreateMutex(NULL, FALSE, mutex_name);
+		if (mutex == NULL)
+			return (ISC_R_UNEXPECTED);
+		if (WaitForSingleObject(mutex, INFINITE) == WAIT_FAILED)
+			return (ISC_R_UNEXPECTED);
+
+		/*
+		 * Recheck need for initialization now that
+		 * the controller is locked.
+		 */
+		if (controller->status == ISC_ONCE_INIT_NEEDED) {
+			function();
+			controller->status = ISC_ONCE_INIT_DONE;
+		}
+
+		ReleaseMutex(mutex);
+		CloseHandle(mutex);
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+#else /* not ISC_ONCE_USE_MUTEX, use InterlockedDecrement instead */
+
+isc_result_t
+isc_once_do(isc_once_t *controller, void(*function)(void))
+
+{
+	REQUIRE(controller != NULL && function != NULL);
+
+	if (controller->status == ISC_ONCE_INIT_NEEDED) {	
+	
+		if (InterlockedDecrement(&controller->counter) == 0) {
+			if (controller->status == ISC_ONCE_INIT_NEEDED) {
+				function();
+				controller->status = ISC_ONCE_INIT_DONE;
+			}
+		} else {
+			while (controller->status == ISC_ONCE_INIT_NEEDED) {
+				/*
+				 * Spin wait.
+				 */
+			}
+		}
+	}
+
+	return (ISC_R_SUCCESS);
+}
+
+#endif /* ISC_ONCE_USE_MUTEX */