This book constitutes the refereed proceedings of the Fourth IEEE International Workshop on Modelling Autonomic Communications Environments, MACE 2009, held in Venice, Italy, in October 2009, as part of the 5th International Week on Management of Networks and Services, Manweek 2009. The 6 full papers and 3 short papers presented together with one invited talk were carefully reviewed and selected from 13 submissions. The papers are organized in topical sections on theory of autonomic management and applying autonomic principles.