Using the notion of complete nonabelian exterior square G ∧G of a pro-p-group G (p prime), we develop the theory of the exterior degree d(G) in the infinite case, focusing on its relations with the probability of commuting pairs d(G). Among the main results of this paper, we describe upper and lower bounds for d(G) with respect to d(G). Here the size of the second homology group H 2 (G, Zp) (over the p-adic integers Zp) plays a fundamental role. A further result of homological nature is placed at the end, in order to emphasize the influence of H 2 (G, Zp) both on G and d(G).