This book constitutes the refereed proceedings of the Third International Conference on Unconventional Models of Computation, UMC 2002, held in Kobe, Japan in October 2002.The 18 revised full papers presented together with eight invited full papers were carefully reviewed and selected from 36 submissions. All major areas of unconventinal computing models are covered, especially quantum computing, DNA computing, membrane computing, cellular computing, and possibilities to break Turing's barrier. The authors address theoretical aspects, practical implementations, as well as philosophical reflections.