A search for B-s(0) -> mu(+)mu(-) and B-0 -> mu(+)mu(-) decays is performed using 1.0 fb(-1) of pp collision data collected at root s = 7 TeV with the LHCb experiment at the Large Hadron Collider. For both decays, the number of observed events is consistent with expectation from background and standard model signal predictions. Upper limits on the branching fractions are determined to be B(B-s(0) -> mu(+)mu(-)) < 4.5(3.8) x 10(-9) and B(B-0 -> mu(+)mu(-)) < 1.0(0.81) x 10(-9) at 95% (90%) confidence level.