This volume contains selected papers from WADT 2008, the 19th International WorkshoponAlgebraicDevelopmentTechniques. Afterhavingjoinedforceswith CMCS for CALCO 2007 in Bergen, WADT took place in 2008 as an individual workshop and in its traditional format. Like its predecessors, WADT 2008 focussed on the algebraic approach to the speci?cation and development of systems, which encompasses many aspects of formal design. Originally born around formal methods for reasoning about abstract data types, WADT now covers new speci?cation frameworks and p- gramming paradigms (such as object-oriented,...