This book constitutes the refereed proceedings of the 4th European Workshop on Case-Based Reasoning, EWCBR-98, held in Dublin, Ireland, in September 1998. The 41 revised full papers presented were carefully selected and reviewed for inclusion in the proceedings. The contributions address the representation and organization of cases in case-bases, the assessment of case similarity, the efficient retrieval of cases from large case-bases, the adaptation of similar case solutions to fit the current problem, case learning and case-base maintenance, and the application of CBR technology to real-world problems.