This volume contains a collection of papers presented at the International Workshop on Semantics for Concurrency, held from 22 to 25 July 1990 at the University of Leicester, UK. The main aim of the workshop was to discuss and seek to identify the positive objective features of the main approaches to semantics for concurrency, and thus to increase understanding between research groups. The field of semantics for concurrency has attracted a number of formalisms, ranging from algebra and automata theory, through logic and topology to category theory. This pluralism provides valuable insight into the nature of concurrency, but when coupled with different views of what issues are important when modelling concurrency, it leads also to disjointed research efforts and lack of communication. Discussions then concentrate on superficial, rather than objective, differences between approaches, and it becomes harder to assess which features of a particular approach are successful in dealing with the problems of concurrent behaviours. This workshop was organized to coordinate research and increase communication. These proceedings include papers on a wide range of issues in concurrency, including: process algebras and equivalences, petri nets, dataflow networks, logics for concurrency, and denotational, partial-order and realtime semantics.