A search for the rare decays B-S(0) -> mu(+)mu(-) and B-0 -> mu(+)mu(-) performed in pp collisions at root s = 7 TeV, with a data sample corresponding to an integrated luminosity of 5 fb(-1) collected by the CMS experiment at the LHC. In both decays, the number of events observed after all selection requirements is consistent with the expectation from background plus standard model signal predictions. The resulting upper limits on the branching fractions are B(B-S(0) -> mu(+)mu(-)) < 7.7 x 10(-9) and B(B-0 -> mu(+)mu(-) ) < 1.8 x 10(-9) at 95\% confidence level.