SUMMARY: Intracellular structures were observed in Candida boidinii grown in a medium containing methanol as the sole source of carbon and energy; these structures were absent in the same organism grown in the presence of glucose or ethanol. These substrate-specific structures are ultrastructurally similar to microbodies. Studies with sphaeroplast lysates and a mutant lacking alcohol-oxidase activity indicate that the alcohol oxidase may be located in these microbodies.