This book constitutes the refereed proceedings of the Second International Conference on COTS-Based Software Systems, ICCBSS 2003, held in Ottawa, Canada in February 2003. The 24 revised full papers presented were carefully reviewed and selected from numerous submissions. The papers address all current issues on commcerial-off-the-shelf-systems, from the point of view of research and development as well as from the practitioner's application point of view.