This book constitutes the refereed proceedings of the Third International Workshop on Parallel Algorithms for Irregularly Structured Problems, IRREGULAR '96, held in Santa Barbara, California, in August 1996.The volume presents 28 revised full papers selected from 51 submissions; also included are one full invited paper by Torben Hagerup and abstracts of four other invited talks. The papers are organized in topical sections on sparse matrix problems, partitioning and domain composition, irregular applications, communication and synchronization, systems support, and mapping and load balancing.