The algebraic specification of abstract data types has beena flourishing research topic in computer science since 1974. The main goal of this work isto evolve theoreticalfoundations and a methodology to support the design andformal development of reliable software. This volume gives the proceedings of the Eighth Workshop onSpecification of Abstract Data Types, held jointly with theThird COMPASS workshop near Paris in August 1991. The maintopics covered by the joint workshop are:- specification languagesand 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 twelvecontributed papers, all of which underwent a carefulrefereeing process.