authors: 1) Karin Erdmann Mathematical Institute, 24-29 St Giles, Oxford, OX1 3LB, UK 2) Miles Holloway Mathematical Institute, 24-29 St Giles, Oxford, OX1 3LB, UK 3) Nicole Snashall Department of Mathematics, University of Leicester LE1 7RH, UK 4) Oyvind Solberg Institutt for Matematiske FAG, NTNU, N-7491 Trondheim, Norway 5)Rachel Taillefer Département de Mathématiques, Faculté des Sciences et Techniques, 23 rue du Docteur Paul Michelon, 42023 Saint-Etienne cedex 2, France. abstract: Support varieties for any finite dimensional algebra over a field were introduced by Snashall-Solberg using graded subalgebras of the Hochschild cohomology ring. We mainly study these varieties for selfinjective algebras under appropriate finite generation hypotheses. Then many of the standard results from the theory of support varieties for finite groups generalize to this situation. In particular, the complexity of the module equals the dimension of its corresponding variety, all closed homogeneous varieties occur as the variety of some module, the variety of an indecomposable module is connected, the variety of periodic modules are lines and for symmetric algebras a generalization of Webb's theorem is true. As a corollary of a more general result we show that Webb's theorem generalizes to finite dimensional cocommutative Hopf algebras. Status: Accepted for publication in K theory. See www.kluweronline.com/issn/0920-3036