This book constitutes the refereed proceedings of the Fourth International Conference on High Performance Embedded Architectures and Compilers, HiPEAC 2009, held in Paphos, Cyprus, in January 2009. The 27 revised full papers presented together with 2 invited keynote paper were carefully reviewed and selected from 97 submissions. The papers are organized in topical sections on dynamic translation and optimisation, low level scheduling, parallelism and resource control, communication, mapping for CMPs, power, cache issues as well as parallel embedded applications.