This book constitutes the thoroughly refereed post-workshop proceedings of the Third International Workshop on Communication, Architecture and Applications for Network-Based Parallel Computing, CANPC '99, held in Orlando, Florida, in January 1999.The 15 revised full papers presented have been carefully reviewed and selected for inclusion in the book. They present the state of the art in network-based parallel computing employing clusters of workstations/PCs connected by off-the-shelf networks for cost-effective high-performance computing.