We classify (up to Morita equivalence) all tame weakly symmetric finite dimensional algebras over an algebraically closed field having simply connected Galois coverings, nonsingular Cartan matrices and the stable Auslander-Reiten quivers consisting only of tubes. In particular, we prove that these algebras have at most four simple modules.1. Introduction and the main results. Throughout the paper K will denote a fixed algebraically closed field. By an algebra we mean a finite dimensional K-algebra with an identity, which we shall assume (without loss of generality) to be basic and connected. For an algebra A, we denote by modA the category of finite dimensional right A-modules and by D the standard duality Hom K (−, K) on modA.From Drozd's remarkable Tame and Wild Theorem [6] the class of algebras may be divided into two disjoint classes. One class consists of tame algebras for which the indecomposable modules occur in each dimension d, in a finite number of discrete and a finite number of one-parameter families. The second class is formed by the wild algebras whose representation theory comprises the representation theories of all finite dimensional K-algebras. Accordingly we may realistically hope to classify the indecomposable finite dimensional modules only for tame algebras.An algebra A is called selfinjective if A ∼ = D(A) in modA, that is, the projective A-modules are injective. Further, A is called symmetric if A and D(A) are isomorphic as A-bimodules. Moreover, A is called weakly symmetric if for any indecomposable projective A-module P the socle soc P of P is isomorphic to its top P / rad P . For a selfinjective algebra A, we denote by s A the stable Auslander-Reiten quiver of A, obtained from the Auslander-Reiten quiver A of A by removing all projective modules and arrows attached to them. A component of s A of the form ZA ∞ /(τ r ), r 1, is called a stable tube of rank r. It is known [13] that a component in s A is a stable tube (of rank r) if and only if it consists of indecomposable periodic modules (of period r) with respect to the action of the Auslander-Reiten translation τ A = D Tr. We also note that τ A = 2 A • N A , where A is the Heller syzygy operator and N A : mod A → mod A is an equivalence induced by the Nakayama automorphism ν A of A. In particular, τ A = 2 A if A is symmetric. Recall also