The algebraic specification of abstract data types has been a flourishing research topic in computer science since 1974. The main goal of this work is to evolve theoretical foundations and a methodology to support the design and formal development of reliable software. This volume gives the proceedings of the Eighth Workshop on Specification of Abstract Data Types, held jointly with the Third COMPASS workshop near Paris in August 1991. The main topics covered by the joint workshop are: - specification languages and program development - algebraic specification of concurrency - theorem proving - object-oriented specifications - order-sorted algebras - abstract implementation and behavioral semantics. The volume contains four invited surveys and twelve contributed papers, all of which underwent a careful refereeing process.