Charged current scattering of ν µ on 12 C has been studied using a π + decayin-flight ν µ beam at the Los Alamos Neutron Science Center. A sample of 66.9 ± 9.1 events satisfying criteria for the exclusive reaction 12 C(ν µ , µ − ) 12 N g.s. was obtained using a large liquid scintillator neutrino detector. The observed flux-averaged cross section (5.6± 0.8± 1.0)× 10 −41 cm 2 agrees well with reliable theoretical expectations. A measurement was also obtained for the inclusive cross section to all accessible 12 N states 12 C(ν µ , µ − )X. This flux-averaged cross section is (10.6 ± 0.3 ± 1.8) × 10 −40 cm 2 which is lower than present theoretical calculations.