This text constitutes the refereed proceedings of the Third International Workshop on Learning Software Organizations, LSO 2001, held in Kaiserslautern, Germany, in September 2001. The 12 revised full papers presented together with an introductory overview, keynote and panel summaries, and three posters were carefully reviewed and selected for inclusion in the book. Among the topics addressed are organizational learning in dynamic domains, knowledge management in software development, Web-based collaborative learning, knowledge management support, software process improvement, Web-based data...