A Bloch-Kato pro-p group G is a pro-p group with the property that the Fp-cohomology ring of every closed subgroup of G is quadratic. It is shown that either such a pro-p group G contains no closed free pro-p groups of infinite rank, or there exists an orientation θ : G → Z × p such that G is θabelian. (See Thm B.) In case that G is also finitely generated, this implies that G is powerful, p-adic analytic with d(G) = cd(G), and its Fp-cohomology ring is an exterior algebra (see Cor. 4.8). These results will be obtained by studying locally powerful groups (see Thm A). There are certain Galois-theoretical implications, since Bloch-Kato pro-p groups arise naturally as maximal pro-p quotients and pro-p Sylow subgroups of absolute Galois groups (see Corollary 4.9). Finally, we study certain closure operations of the class of Bloch-Kato pro-p groups, connected with the Elementary type conjecture.