This volume contains the papers accepted for the 4th Workshop on Algorithm Engineering (WAE 2000) held in Saarbruc ¨ ken, Germany, during 5–8 September 2000, together with the abstract of the invited lecture given by Karsten Weihe. The Workshop on Algorithm Engineering covers research on all aspects of the subject. The goal is to present recent research results and to identify and explore directions for future research. Previous meetings were held in Venice (1997), Saarbruc ¨ ken (1998), and London (1999). Papers were solicited describing original research in all aspects of algorithm engineering, including: – Development of software repositories and platforms which allow the use of and experimentation with e?cient discrete algorithms. – Novel uses of discrete algorithms in other disciplines and the evaluation of algorithms for realistic environments. – Methodological issues including standards in the context of empirical - search on algorithms and data structures. – Methodological issues regarding the process of converting user requirements into e?cient algorithmic solutions and implementations. The program committee accepted 16 from a total of 30 submissions. The program committee meeting was conducted electronically. The criteria for sel- tion were originality, quality, and relevance to the subject area of the workshop. Considerable e?ort was devoted to the evaluation of the submissions and to p- viding the authors with feedback. Each submission was reviewed by at least four program committee members (assisted by subreferees). A special issue of the ACM Journal of Experimental Algorithmics will be devoted to selected papers from WAE 2000.