diff --git a/dlls/kernel/process.c b/dlls/kernel/process.c
index 32aa36e7541..15c9380bd5f 100644
--- a/dlls/kernel/process.c
+++ b/dlls/kernel/process.c
@@ -405,18 +405,9 @@ BOOL WINAPI SetProcessPriorityBoost(HANDLE hprocess,BOOL disableboost)
 BOOL WINAPI ReadProcessMemory( HANDLE process, LPCVOID addr, LPVOID buffer, SIZE_T size,
                                SIZE_T *bytes_read )
 {
-    DWORD res;
-
-    SERVER_START_REQ( read_process_memory )
-    {
-        req->handle = process;
-        req->addr   = (void *)addr;
-        wine_server_set_reply( req, buffer, size );
-        if ((res = wine_server_call_err( req ))) size = 0;
-    }
-    SERVER_END_REQ;
-    if (bytes_read) *bytes_read = size;
-    return !res;
+    NTSTATUS status = NtReadVirtualMemory( process, addr, buffer, size, bytes_read );
+    if (status) SetLastError( RtlNtStatusToDosError(status) );
+    return !status;
 }
 
 
@@ -426,46 +417,9 @@ BOOL WINAPI ReadProcessMemory( HANDLE process, LPCVOID addr, LPVOID buffer, SIZE
 BOOL WINAPI WriteProcessMemory( HANDLE process, LPVOID addr, LPCVOID buffer, SIZE_T size,
                                 SIZE_T *bytes_written )
 {
-    static const int zero;
-    unsigned int first_offset, last_offset, first_mask, last_mask;
-    DWORD res;
-
-    if (!size)
-    {
-        SetLastError( ERROR_INVALID_PARAMETER );
-        return FALSE;
-    }
-
-    /* compute the mask for the first int */
-    first_mask = ~0;
-    first_offset = (unsigned int)addr % sizeof(int);
-    memset( &first_mask, 0, first_offset );
-
-    /* compute the mask for the last int */
-    last_offset = (size + first_offset) % sizeof(int);
-    last_mask = 0;
-    memset( &last_mask, 0xff, last_offset ? last_offset : sizeof(int) );
-
-    SERVER_START_REQ( write_process_memory )
-    {
-        req->handle     = process;
-        req->addr       = (char *)addr - first_offset;
-        req->first_mask = first_mask;
-        req->last_mask  = last_mask;
-        if (first_offset) wine_server_add_data( req, &zero, first_offset );
-        wine_server_add_data( req, buffer, size );
-        if (last_offset) wine_server_add_data( req, &zero, sizeof(int) - last_offset );
-
-        if ((res = wine_server_call_err( req ))) size = 0;
-    }
-    SERVER_END_REQ;
-    if (bytes_written) *bytes_written = size;
-    {
-        char dummy[32];
-        SIZE_T read;
-        ReadProcessMemory( process, addr, dummy, sizeof(dummy), &read );
-    }
-    return !res;
+    NTSTATUS status = NtWriteVirtualMemory( process, addr, buffer, size, bytes_written );
+    if (status) SetLastError( RtlNtStatusToDosError(status) );
+    return !status;
 }
 
 
diff --git a/dlls/ntdll/ntdll.spec b/dlls/ntdll/ntdll.spec
index 66a81301d88..a48075c07f3 100644
--- a/dlls/ntdll/ntdll.spec
+++ b/dlls/ntdll/ntdll.spec
@@ -186,7 +186,7 @@
 @ stub NtRaiseHardError
 @ stdcall NtReadFile(long long long long long long long long long)
 @ stub NtReadRequestData
-@ stub NtReadVirtualMemory
+@ stdcall NtReadVirtualMemory(long ptr ptr long ptr)
 @ stub NtRegisterNewDevice
 @ stdcall NtRegisterThreadTerminatePort(ptr)
 @ stub NtReleaseMutant
@@ -257,7 +257,7 @@
 @ stub NtWaitLowEventPair
 @ stdcall NtWriteFile(long long ptr ptr ptr ptr long ptr ptr)
 @ stub NtWriteRequestData
-@ stub NtWriteVirtualMemory
+@ stdcall NtWriteVirtualMemory(long ptr ptr long ptr)
 @ stub PfxFindPrefix
 @ stub PfxInitialize
 @ stub PfxInsertPrefix
@@ -717,7 +717,7 @@
 @ stub ZwRaiseHardError
 @ stdcall ZwReadFile(long long long long long long long long long) NtReadFile
 @ stub ZwReadRequestData
-@ stub ZwReadVirtualMemory
+@ stdcall ZwReadVirtualMemory(long ptr ptr long ptr) NtReadVirtualMemory
 @ stub ZwRegisterNewDevice
 @ stdcall ZwRegisterThreadTerminatePort(ptr) NtRegisterThreadTerminatePort
 @ stub ZwReleaseMutant
@@ -786,7 +786,7 @@
 @ stub ZwWaitLowEventPair
 @ stdcall ZwWriteFile(long long ptr ptr ptr ptr long ptr ptr) NtWriteFile
 @ stub ZwWriteRequestData
-@ stub ZwWriteVirtualMemory
+@ stdcall ZwWriteVirtualMemory(long ptr ptr long ptr) NtWriteVirtualMemory
 @ cdecl _CIpow() NTDLL__CIpow
 @ stub __eCommonExceptions
 @ stub __eEmulatorInit
diff --git a/dlls/ntdll/virtual.c b/dlls/ntdll/virtual.c
index 8e2f20131ab..a656ae69cba 100644
--- a/dlls/ntdll/virtual.c
+++ b/dlls/ntdll/virtual.c
@@ -1542,3 +1542,66 @@ NTSTATUS WINAPI NtFlushVirtualMemory( HANDLE process, LPCVOID *addr_ptr,
     if (!msync( addr, *size_ptr, MS_SYNC )) return STATUS_SUCCESS;
     return STATUS_NOT_MAPPED_DATA;
 }
+
+
+/***********************************************************************
+ *             NtReadVirtualMemory   (NTDLL.@)
+ *             ZwReadVirtualMemory   (NTDLL.@)
+ */
+NTSTATUS WINAPI NtReadVirtualMemory( HANDLE process, const void *addr, void *buffer,
+                                     SIZE_T size, SIZE_T *bytes_read )
+{
+    NTSTATUS status;
+
+    SERVER_START_REQ( read_process_memory )
+    {
+        req->handle = process;
+        req->addr   = (void *)addr;
+        wine_server_set_reply( req, buffer, size );
+        if ((status = wine_server_call( req ))) size = 0;
+    }
+    SERVER_END_REQ;
+    if (bytes_read) *bytes_read = size;
+    return status;
+}
+
+
+/***********************************************************************
+ *             NtWriteVirtualMemory   (NTDLL.@)
+ *             ZwWriteVirtualMemory   (NTDLL.@)
+ */
+NTSTATUS WINAPI NtWriteVirtualMemory( HANDLE process, void *addr, const void *buffer,
+                                      SIZE_T size, SIZE_T *bytes_written )
+{
+    static const unsigned int zero;
+    unsigned int first_offset, last_offset, first_mask, last_mask;
+    NTSTATUS status;
+
+    if (!size) return STATUS_INVALID_PARAMETER;
+
+    /* compute the mask for the first int */
+    first_mask = ~0;
+    first_offset = (unsigned int)addr % sizeof(int);
+    memset( &first_mask, 0, first_offset );
+
+    /* compute the mask for the last int */
+    last_offset = (size + first_offset) % sizeof(int);
+    last_mask = 0;
+    memset( &last_mask, 0xff, last_offset ? last_offset : sizeof(int) );
+
+    SERVER_START_REQ( write_process_memory )
+    {
+        req->handle     = process;
+        req->addr       = (char *)addr - first_offset;
+        req->first_mask = first_mask;
+        req->last_mask  = last_mask;
+        if (first_offset) wine_server_add_data( req, &zero, first_offset );
+        wine_server_add_data( req, buffer, size );
+        if (last_offset) wine_server_add_data( req, &zero, sizeof(int) - last_offset );
+
+        if ((status = wine_server_call( req ))) size = 0;
+    }
+    SERVER_END_REQ;
+    if (bytes_written) *bytes_written = size;
+    return status;
+}
diff --git a/include/winternl.h b/include/winternl.h
index b8ed742e68d..b18e1668297 100644
--- a/include/winternl.h
+++ b/include/winternl.h
@@ -977,6 +977,7 @@ NTSTATUS  WINAPI NtQueryValueKey(HKEY,const UNICODE_STRING *,KEY_VALUE_INFORMATI
 NTSTATUS  WINAPI NtQueryVirtualMemory(HANDLE,LPCVOID,MEMORY_INFORMATION_CLASS,PVOID,ULONG,ULONG*);
 void      WINAPI NtRaiseException(PEXCEPTION_RECORD,PCONTEXT,BOOL);
 NTSTATUS  WINAPI NtReadFile(HANDLE,HANDLE,PIO_APC_ROUTINE,PVOID,PIO_STATUS_BLOCK,PVOID,ULONG,PLARGE_INTEGER,PULONG);
+NTSTATUS  WINAPI NtReadVirtualMemory(HANDLE,const void*,void*,SIZE_T,SIZE_T*);
 NTSTATUS  WINAPI NtReleaseSemaphore(HANDLE,ULONG,PULONG);
 NTSTATUS  WINAPI NtReplaceKey(POBJECT_ATTRIBUTES,HKEY,POBJECT_ATTRIBUTES);
 NTSTATUS  WINAPI NtResetEvent(HANDLE,PULONG);
@@ -1003,6 +1004,7 @@ NTSTATUS  WINAPI NtUnmapViewOfSection(HANDLE,PVOID);
 NTSTATUS  WINAPI NtWaitForSingleObject(HANDLE,BOOLEAN,const LARGE_INTEGER*);
 NTSTATUS  WINAPI NtWaitForMultipleObjects(ULONG,const HANDLE*,BOOLEAN,BOOLEAN,const LARGE_INTEGER*);
 NTSTATUS  WINAPI NtWriteFile(HANDLE,HANDLE,PIO_APC_ROUTINE,PVOID,PIO_STATUS_BLOCK,const void*,ULONG,PLARGE_INTEGER,PULONG);
+NTSTATUS  WINAPI NtWriteVirtualMemory(HANDLE,void*,const void*,SIZE_T,SIZE_T*);
 
 void      WINAPI RtlAcquirePebLock(void);
 BYTE      WINAPI RtlAcquireResourceExclusive(LPRTL_RWLOCK,BYTE);