Clusters of workstations/PCs connected by o?-the-shelf networks have become popular as platforms for cost-e?ective parallel computing. Technological - vances in both hardware and software have made such a network-based parallel computingplatform an a?ordable alternative to commercial supercomputers for an increasing number of scienti?c applications. Continuing in the tradition of the three previously successful workshops, this fourth Workshop on Communication, Architecture and Applications for Network-basedParallelComputing(CANPC 2000)broughttogetherresearchers and practitioners working in architecture, system software, applications, and performance evaluation to discuss state-of-the-art solutions for network-based parallel computing. This year, the workshop was held in conjunction with the sixth International Symposium on High-Performance Computer Architecture (HPCA-6). As in prior editions, the papers presented here are representative of a sp- trum of research e?orts from groups in academia and industry to further - prove cluster computing's viability, performance, cost-e?ectiveness, and usab- ity. Speci?cally, we have arranged the contributions in this edition into four groups: (1) program development and execution support, (2) network router - chitecture, (3) system support for communication abstractions, and (4) network software and interface architecture.