We determine the mod-p cohomology ring and some of the integral cohomology ring structure of a p-group expressible as an extension with kernel cyclic of order p and quotient C p m 0 C p n, where m, n > 1. § 1. IntroductionLet p denote an odd prime and let P m n be the group with presentation of the formwhere m, n > 1. We may express P m n as a central extension of the formwhere C = = C p and L = (A, B} = C p m X C p n. In this paper we shall determine the mod-p cohomology ring and some of the integral cohomology ring structure of P m n when m,n>l. For the case when m = n = 1, P ltl is the non-abelian group of order p 3 and exponentp, and the integral and mod-p cohomology rings of P l { are known (see [4], [5], [7]). We note that for £ = 3 and m, n > 1, Leary in [6] has obtained the Poincare series of H*(P m n , F 3 ). Let G = P m> " where m, n > 1. It is clear that we may assume, without loss of generality, that m > n > 2. In section 2 of this paper we shall review some facts on Massey products. Then in section 3, we shall use Massey products to define some generators of degree two in the mod-p cohomology ring of G and to determine some of the relations involving these generators. This explicit use of Massey products to obtain the cohomology ring structure has been demonstrated by Leary in [3] and [5]. We remark here that the mod-p cohomology ring structure of G