Thanks Xiaomeng. I had everything except using Evolve for the class in the run configuration. For some reason I thought I needed the tutorial1 file MaxOnes.java in there. Obviously the parameter file must handle this linkage. For any others needing to know this is how I did it... 1. Create a new project called ecj, - select Use project folder as root for sources and class files - click Finish 2. Right click on the ecj folder and select Import... - click on the File System folder and click Next - Browse for the ec folder from the downloaded archive, mine was C:\ecj\ec <-- you want the files from the ec folder - click on the check box beside the ec folder to select all the files - click on the Create top-level folder check box and click Finish open the ecj project and you'll see all subfolders have ec. referencing 3. To set up the run configuration (tutorial1 given) - click on Run (main menu) Run Configurations... - under Java Application click on the New button - type in a Name, tutorial1 - for the Main class: type ec.Evolve - click on the Arguments tab - in the Program arguments box type in, -file ec/app/tutorial1/tutorial1.params - click Apply 4. To try out tutorial1 click on Run - you'll get an error message if Eclipse is set up that way - look in your console window for output -- ray