Reaction of laser-ablated Mo atoms with CH4 in excess argon forms the CH3-MoH, CH2=MoH2, and CH&3bond; MoH3 molecules, which are identified from infrared spectra by isotopic substitution and density functional theory frequency calculations. These simple methyl, methylidene, and methylidyne molybdenum hydride molecules are reversibly interconverted by a-H transfers upon visible and ultraviolet irradiations. The methylidene dihydride CH2=MoH2 exhibits CH2 and MoH2 distortion and agostic interaction to a lesser degree than CH2=ZrH2. Molybdenum methylidyne trihydride CH&3bond; MoH3 is a stable C-3v symmetry molecule.