Index: rostests/apitests/kernel32/CMakeLists.txt
===================================================================
--- rostests/apitests/kernel32/CMakeLists.txt	(revision 74717)
+++ rostests/apitests/kernel32/CMakeLists.txt	(working copy)
@@ -14,6 +14,7 @@
     GetDriveType.c
     GetModuleFileName.c
     interlck.c
+    IsDBCSLeadByteEx.c
     LoadLibraryExW.c
     lstrcpynW.c
     lstrlen.c
Index: rostests/apitests/kernel32/IsDBCSLeadByteEx.c
===================================================================
--- rostests/apitests/kernel32/IsDBCSLeadByteEx.c	(nonexistent)
+++ rostests/apitests/kernel32/IsDBCSLeadByteEx.c	(working copy)
@@ -0,0 +1,74 @@
+/*
+ * PROJECT:         ReactOS api tests
+ * LICENSE:         GPLv2+ - See COPYING in the top level directory
+ * PURPOSE:         Tests for IsDBCSLeadByteEx
+ * PROGRAMMER:      Katayama Hirofumi MZ <katayama.hirofumi.mz@gmail.com>
+ */
+
+#include <apitest.h>
+
+#define WIN32_NO_STATUS
+#define _INC_WINDOWS
+#define COM_NO_WINDOWS_H
+#include <stdio.h>
+#include <winnls.h>
+
+START_TEST(IsDBCSLeadByteEx)
+{
+    static const char *names[] = {
+        "ChineseSimpilifed",
+        "ChineseTraditional",
+        "Japanese",
+        "Korean"
+    };
+    static const WORD codepages[] = { 936, 950, 932, 949 };
+
+    int i, k, k0, count, array[8], flag;
+
+    for (i = 0; i < _countof(codepages); ++i)
+    {
+        count = 0;
+        ZeroMemory(&array, sizeof(array));
+
+        k0 = 0;
+        flag = 0;
+        for (k = 0; k <= 256; ++k)
+        {
+            if (flag)
+            {
+                if (!IsDBCSLeadByteEx(codepages[i], k))
+                {
+                    array[count++] = k0;
+                    array[count++] = k - 1;
+                    flag = 0;
+                }
+            }
+            else
+            {
+                if (IsDBCSLeadByteEx(codepages[i], k))
+                {
+                    k0 = k;
+                    flag = 1;
+                }
+            }
+        }
+
+        switch (i)
+        {
+        case 0:
+        case 1:
+        case 3:
+            ok(count == 2, "%s: count expected 2, was %d\n", names[i], count);
+            ok(array[0] == 0x81, "%s: array[0] was %d\n", names[i], array[0]);
+            ok(array[1] == 0xFE, "%s: array[1] was %d\n", names[i], array[1]);
+            break;
+        case 2:
+            ok(count == 4, "%s: count expected 4, was %d\n", names[i], count);
+            ok(array[0] == 0x81, "%s: array[0] was %d\n", names[i], array[0]);
+            ok(array[1] == 0x9F, "%s: array[1] was %d\n", names[i], array[1]);
+            ok(array[2] == 0xE0, "%s: array[2] was %d\n", names[i], array[2]);
+            ok(array[3] == 0xFC, "%s: array[3] was %d\n", names[i], array[3]);
+            break;
+        }
+    }
+}
Index: rostests/apitests/kernel32/testlist.c
===================================================================
--- rostests/apitests/kernel32/testlist.c	(revision 74717)
+++ rostests/apitests/kernel32/testlist.c	(working copy)
@@ -15,6 +15,7 @@
 extern void func_GetDriveType(void);
 extern void func_GetModuleFileName(void);
 extern void func_interlck(void);
+extern void func_IsDBCSLeadByteEx(void);
 extern void func_LoadLibraryExW(void);
 extern void func_lstrcpynW(void);
 extern void func_lstrlen(void);
@@ -42,6 +43,7 @@
     { "GetDriveType",                func_GetDriveType },
     { "GetModuleFileName",           func_GetModuleFileName },
     { "interlck",                    func_interlck },
+    { "IsDBCSLeadByteEx",            func_IsDBCSLeadByteEx },
     { "LoadLibraryExW",              func_LoadLibraryExW },
     { "lstrcpynW",                   func_lstrcpynW },
     { "lstrlen",                     func_lstrlen },