Methyl mercaptan and by-product thiophene can be obtained from the reaction of CO/H-2/H2S mixtures over alpha-Al2O3 at 340 degreesC, and selectivities of methyl mercaptan of greater than or equal to 98% can be readily obtained in a sustained reaction. gamma-Al2O3 and Cr2O3 were also found to be active catalysts and gave high selectivities to methyl mercaptan, although these catalysts gave (CH3)(2)S as by-product rather than thiophene. In the absence of H2S, all the catalysts displayed virtually no catalytic activity.