Abstract: Graphs of groups encode group actions on trees, and have many applications in algebra and geometric group theory. A graph of groups G consists of a graph (V,E) together with a group G_v for each vertex v in V and a group G_e for each edge e in E, so that G_e includes into G_v for v the range and source of e. The graph of groups G has a fundamental group which acts on its universal covering tree T, and thus acts on the boundary of T. Under mild assumptions, we associate a C* algebra to G and investigate its properties. This is joint work with Nathan Brownlowe, Alex Mundey, David Pask and Jack Spielberg.