With the appearance of powerful parallel computers, increased attention has been paid to algorithms which rely upon analogies to natural processes. Recent developments in this field were discussed at a workshop held in Dortmund in 1990, whose proceedings are presented in this volume. The subjects treated include Darwinian methods such as evolution strategies and genetic algorithms, Boltzmann methods such as simulated annealing, classifier systems and neural networks, and the transfer of natural metaphors to artificial problem-solving. The main objectives of the conference were to gather theoretical results about these algorithms, to discuss various implementations on different parallel computer architectures, and to summarize the state of the art in the field.