Java Decompiler (JD) is generally recommended as a good, well, Java Decompiler. JD-Eclipse is the Eclipse plugin for JD. I had problems on several different machines to get the plugin running. Whenever I tried to open a .class file, the standard "Source not found" editor would show, displaying lowlevel bytecode disassembly, not the Java source output you'd expect from a decompiler. Installation docs in http://java.decompiler.free.fr/?q=jdeclipse are not bad but quite vague when it comes to troubleshooting. Opening this question to collect additional information: What problems did you encounter before JD was running in Eclipse Helios? What was the solution?