I ocassionally got the same thing too! Still don't know what causes it. Most of the time a programs works fine, but suddenlly it returns this message (probably after a did something, but I can't recall). I thought that's my machine's problem, Now I think it might not be that simple. BTW, I have both jdk1.2 and MS SDK 3.1 and MS VM (latest) installed. Any pointer?? Thanks. Patrick. -----Original Message----- From: Ozer Irfan [mailto:[EMAIL PROTECTED]] Sent: Wednesday, February 17, 1999 6:23 AM To: Carl H. Sayres Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED] Subject: problem jdk1.2 I have this message Exception in thread "main' java.lang.NoClassDefFoundError when I run java test1 With javac I don't have problems this is the program import java.io.* ; public class test1 { public static void main(String args []) { System.out.println("Hello"); } } Thanks