This volume contains 15 thoroughly refereed full research papers selected from the presentations given during two workshops on constraint processing; these workshops were held in conjunction with the International Congress on Computer Systems and Applied Mathematics (St. Petersburg, Russia, July 1993) and the European Conference on Artificial Intelligence (Amsterdam, The Netherlands, August 1994).This volume essentially contributes to integrating the different approaches to the young and very active field of constraint processing by offering papers from logic programming, knowledge representation, expert systems, theoretical computer science, operations research, and other fields. Among contributions are two surveys, by Podelski and van Roy and by Freuder.