For maximum security, the J/Direct methods defined in the com.ms.win32 package do perform the call stack check on each invocation. If you are using these classes for a Java application (running under JVIEW or WJVIEW), the performance overhead will be negligible. If you are using com.ms.win32 classes from a trusted class and require maximum performance, you should copy the required J/Direct declarations into your own classes and disable the per-invocation security check. See Security Checks upon Every Invocation for more information on disabling the per-invocation security check.