This book constitutes the proceedings of the Fifth European Performance Engineering Workshop, EPEW 2008, held in Palma de Mallorca, Spain, in September 24-25, 2008. The 17 papers presented in this volume, together with abstracts of 2 invited papers, were carefully reviewed and selected from 39 submissions. The topics covered are software performance engineering; stochastic process algebra and SANs; performance query specification and measurement; computer and communications networks; queueing theory and Markov chains; and applications.