Here are the refereed proceedings of the Third International Workshop on Web Services and Formal Methods, WS-FM 2006, held in conjunction with the Fourth International Conference on Business Process Management, BPM 2006. The book presents 15 revised full papers and 3 invited lectures covering such topics as protocols and standards for WS; languages and description methodologies for Coreography/Orchestration/Workflow; coordination techniques for WS; security, performance evaluation and quality of service, and more.