Methanol has been known to be oxidized by liver alcohol dehydrogenase (ADH) and catalase enzymes. The data presented here indicate that this primary alcohol is also metabolized by rat liver mixed function oxidase (MFO) induced by phenobarbital. Comparative studies on the oxidation of methanol and N-demethylation of benzphetamine by MFO reveal that SKF 525-A inhibits both reactions whereas aminotriazole, a known inhibitor of catalase, abolishes the activity of microsomal methanol oxidase with no effect on N-demethylase. While disulfiram depresses N-demethylase activity, pyrazole and cyanide have little or no effect on the microsomal enzyme activity. Although ethanol appears to be a competitive inhibitor of microsomal methanol oxidase it is a poor inhibitor of this enzyme system.