This book constitutes the refereed proceedings of the Joint Modular Languages Conference, JMLC'97, held in Linz, Austria, in March 1997.The 24 revised full papers presented were carefully selected from a total of 55 submissions; also included are full papers of two invited presentations. The book is devoted to languages, techniques, and tools for the development of modular, extensible, and type-safe software systems. Among the programming languages covered are Modula, Oberon, Ada95, Eiffel, Salher, Java, and others. The issues addressed include compiler technology, persistence, data structures, typing, distribution, active objects, real-time programming, inheritance, reflection, languages, etc.