This volume constitutes the refereed proceedings of the 5th International AMAST Workshop on Formal Methods for Real Time and Probabilistic Systems (ARTS '99) held in Bamberg, Germany in May 1999. The 17 revised full papers presented together with three invited contributions were reviewed and selected from 33 submissions. The papers are organized in topical sections on verification of probabilistic systems, model checking for probabilistic systems, semantics of probabilistic process calculi, semantics of real time processes, real time compilation, stochastic process algebra, and modeling and...