The algebraic approach to system speci?cation and development, born in the 1970sas a formalmethod for abstractdata types, encompassestoday the formal design of integrated hardware and software systems, new speci?cation fra- works and programming paradigms (such as object-oriented, logic, and high- order functional programming) and a wide range of application areas (including information systems, concurrent and distributed systems). Workshops on Al- braicDevelopmentTechniques,initiatedin1982asWorkshopsonAbstractData Types, have become a prominent forum to present and discuss research on this important area. The 14th International Workshop on Algebraic Development Techniques (WADT'99) took place at the Chat eau de Bonas, near Toulouse, September 15-18,1999,and was organized by Didier Bert and Christine Choppy. The main topics of the workshop were: - algebraic speci?cation - other approaches to formal speci?cation - speci?cation languages and methods - term rewriting and proof systems - speci?cation development systems (concepts, tools, etc.). The program consisted of invited talks by Michel Bidoit, Manfred Broy, Bart Jacobs, Natarajan Shankar, and 69 presentations describing ongoing - search. The parallel sessions were devoted to: algebraic speci?cations and other speci?cation formalisms, test and validation, concurrent processes, - plications, logics and validation, combining formalisms, subsorts and parti- ity, structuring, rewriting, coalgebras and sketches, re?nement, institutions and categories, ASM speci?cations. There were also sessions re?ecting - going research achieved in the Common Framework Initiative (CoFI, see http://www.brics.dk/Projects/CoFI/), within its di?erent task groups: CASL (Common Algebraic Speci?cation Language), CASL semantics, CASL tools, methodology, and reactive systems.