We have searched for second-generation leptoquark (LQ) pairs in the μμ+jets channel using 94 ±5pb−1 of ¯pp collider data collected by the D0 experiment at the Fermilab Tevatron during 1993–1996. No evidence for a signal is observed. These results are combined with those from the μν+jets and νν+jets channels to obtain 95% confidence level (C.L.) upper limits on the LQ pair production cross section as a function of mass and β, the branching fraction of a LQ decay into a charged lepton and a quark. Lower limits of 200(180)GeV/c2 for β=1(1/2) are set at the 95% C.L. on the mass of scalar LQ. Mass limits are also set on vector leptoquarks as a function of β.