A search for the decays Bs0 -> mu(+)mu(-) and B0 -> mu(+)mu(-) is performed with about 37 pb(-1) of pp collisions at root s = 7 TeV collected by the LHCb experiment at the Large Hadron Collider at CERN. The observed numbers of events are consistent with the background expectations. The resulting upper limits on the branching ratios are B(B-s(0) -> mu(+)mu(-) ) <5.6 x 10(-8) and B(B0 -> mu(+)mu(-) ) <1.5 x 10(-8) at 95% confidence level. (C) 2011 CERN. Published by Elsevier B.V. All rights reserved.