Generative and component approaches have the potential to revolutionize so- waredevelopmentinasimilarwayasautomationandcomponentsrevolutionized manufacturing. Generative Programming (developing programs that synthesize other programs), Component Engineering (raising the level of modularization and analysis in application design), and Domain-Speci?c Languages (elevating program speci?cations to compact domain-speci?c notations that are easier to write and maintain) are key technologies for automating program development. GPCE arose as a joint conference, merging the prior conference on Gene- tive and Component-Based SoftwareEngineering (GCSE) and the Workshop on Semantics, Applications, and Implementation of Program Generation (SAIG). Thegoalof GPCEisto providea meeting placefor researchersandpractitioners interested in cutting edge approachesto software development. We aim to foster further cross-fertilization between the software engineering research community on the one hand, and the programming languages community on the other, in addition to supporting the original research goals of both the GCSE and the SAIG communities. This volume contains the proceedings of the Third International Conference on Generative Programming and Component Engineering, held in Vancouver, Canada from October 24 to 28, 2004, where it was co-located with OOPSLA 2004 and ISSM 2004.