In the last few years investigations about the spectra of RIEMANNian manifolds, their cohomology and the connection t o multiplicities, with which certain representations occur in others, were intensively carried out.In the sixties some papers [7], [8], [9] of the Japanese mathematicians MAT-SUSHIMA and MURAKAMI were published. There they dealt with the theory of harmonic forms and the investigations of some special cohomology groups.In 1967, the paper [12] of MATSUSHIMA was published. He considered a connected semi-simple LTE group G with finite center and only non-compact simple components, a maximal compact subgroup K of G, the symmetric space X =GIK and a discrete subgroup I' of G such that r\G is compact and r acts freely on X.Then MATSUSHIMA praved a formula for the dimension of the space of all harmonic r-invariant p-forms on X , where he related this dimension to the decomposition of the right-regular unitary representation of G into L*(I'\G). Finally he considered an example. In this paper the formula of MATSUSHIMA will be generalized to a formula for the dimension of eigensubspaces of the laplacian operator to an arbitrary eigenvalue il of T-invariant p-forms on X . Here this dimension will be related to the decomposition of the right-regular representation of G into LZ(r\G), too. This main result is formulated in Theorem 5.1 of section 5. For A = O we get the formula of MATSUSHIMA as a special case.In soction 1 the general situation, which is our starting-point, will be described. A regularity-and a finiteness-proposition for the Iaplacian operator is mentioned and tho CASIWK. operator for a unitary representation will be defined in section 2. Section 3 contains a connection between T-invariant differential p-forms on the quotient G/K and determined vector-valued functions on r\G. This connection playg an important role in the proof of our main result. In section 4 we will prove the decomposition proposition for the right-regular representation of G in L2(r\Q) (following GELFAND [l]). As mentioned, the main result will be described in section 5. Its detailed proof will be given in section 6.