The synthesis alcohol-oxidase[EC 1.1.3.13] was investigated in the yeasts, Candida boidinii CBS 8106 and C. boidinii CBS 2428, during growth on different carbon sources. Alcohol-oxidase was undetectable in all strains submitted to the test in the mineral salts medium containing 1.0% glucose, but its production was rapidly increased when the carbon source was changed glucose to 1.0% methanol after 24hrs of incubation. When cells were grown on the various carbon sources (glucose, xylose, lactose, glycerol, galactose, saccharose, sorbose, lactic acid or acetic acid), the alcohol-oxidase activity was undetected. These carbon sources together with methanol yielded far better synthesis of alcohol-oxidase than in the case of carbon sources alone. Alcohol-oxidase was active towards alcohol of shorter alkyl-chain length than C5 and unsaturated alcohols. Its affinity for these alcohols decreased with the increasing length of the alkyl-chain. The apparent Km values for the methanol of Candida boidinii CBS 8106 and C. boidinii CBS 2428 were 1.96 and 1.21, respestively.