This book constitutes the refereed proceedings of the 13th International Working Conference on Requirements Engineering: Foundation for Software Quality, REFSQ 2007, held in Trondheim, Norway in June 2007. The 27 revised full papers presented together with 1 keynote lecture were carefully reviewed and selected from numerous submissions for inclusion in the book. The papers are organized in thematic sections on goal-driven requirements engineering (RE), products and product-lines, value-based RE and the value of RE, requirements elicitation, requirements specification, industrial experience of RE, and requirements quality and quality requirements. Within these themes, the work presented spanned a range of application domains from business systems to air traffic management, used techniques that varied from ethno-methodology to formal specification and delivered requirements for both custom systems and software product lines.