An in situ infrared spectroscopic study was conducted to elucidate the reaction pathways for low-temperature methanol synthesis in a catalytic system composed of Ni(CO)(4) and CH3OK (denoted as Ni(CO)(4)CH3OK). The reaction was conducted in a liquid medium at 313-333 K with an initial pressure of 3.0 MPa. When CH3OK was added to Ni(CO)4 Solution at 293 K, different carbonylnickelates, [Ni-5(CO)(12)](2-), [Ni-6(CO)(12)](2-) and [Ni(CO)(3)(COOCH3)](-), were immediately formed from Ni(CO)4. The species and the composition of the carbonylnickel complexes varied with temperature. The variations in concentrations of methanol (MeOH) and methyl formate (MF) during the run, which were determined from their IR absorptions, indicated a pattern characteristic of consecutive reactions with MF as an intermediate. Thus, it was shown that methanol was produced through the carbonylation of MeOH to MF and the subsequent hydrogenation of NIF to MeOH. Stable hydridocarbonylnickel anions, [HNi(CO)(3)](-) and/or [HNTi2(CO)(6)](-), were observed together with a small amount of Ni(CO)(4) throughout the methanol synthesis. Since NTi(CO)(4) alone showed no activity for the hydrogenation of MF the hydridocarbonylnickel anions generated in the presence of CH3OK must be responsible for the reaction. The dual role of CH3OK in the catalytic system was stated.