th This volume contains the proceedings of AMAST 2008, the 12 International Conference on Algebraic Methodology and Software Technology, held during July 28-31, 2008, in Urbana, Illinois, USA. The major goal of the AMAST conferences is to promote research toward settingsoftwaretechnologyona?rm, mathematicalbasis.Worktowardthisgoal isacollaborative, internationale?ortwithcontributionsfrombothacademiaand industry. The envisioned virtues of providing software technology developed on a mathematical basis include: correctness, which can be proved mathematically; safety, so that developed software...