This book constitutes the proceedings of the Third International Workshop on Multiple Access Communications, MACOM 2010, held in Barcelona, Spain, in September 2010. The 21 full papers and 6 poster papers presented were carefully reviewed and selected from 40 submissions. They are divided in topical sections on medium access control, multiuser detection and advanced coding techniques, queuing systems, wireless mesh networks and WIMAX, advanced topics in wireless networks, and mobile ad-hoc networks.