Dear IDL Experts, I appreciate your suggestions for figuring out how to add a path permanently. To insert a new path I use: Windows->Preferences->IDL->Paths->Insert. The path stays there for a session then it disappears. Mostly, I had to add the new path each time when I open IDL.. I also tried a startup file (under Windows->Preferences->IDL->Startup File), that adds this directory to the path but looks like IDL does not care about startup file. My startup file has a line: !PATH = !PATH + PATH_SEP(/Search_Path) + Expand_Path('+C:\Users\......\IDL\IDLLib\') Best regards, - Nevzat