Catechol methyltransferase (S-adenosyl-L-methionine : catechol O-methyltransferase; EC 2.1.1.6) was localized immunocytochemically in the yeast Candida tropicalis by the unlabelled antibody enzyme method, involving soluble peroxidase-antiperoxidase complex. Immunoreactivity was detected by light and electron microscopy in the outer layer of the cell wall and at the plasma membrane. The possible function of the methyltransferase in C. tropicalis id discussed.