This book constitutes the refereed proceedings of the First European Workshop on Software Architecture, EWSA 2004, held in St Andrews, Scotland, UK in May 2004 in conjunction with ICSE 2004. The 9 revised full research papers, 4 revised full experience papers, and 6 revised position papers presented together with 5 invited presentations on ongoing European projects on software architectures were carefully reviewed and selected from 48 submissions. All current aspects of software architectures are addressed ranging from foundational and methodological issues to application issues of practical relevance.