We used polyacrylamide slab gel electrophoresis with specific staining for seven enzymes to compare 108 strains belonging to the genera Rhodotorula and Rhodosporidium. The patterns obtained allowed us to divide the strains of Rhodotorula glutinis and its varieties into six groups. The strains of Rhodotorula rubra and Rhodotorula pilimanae examined had identical patterns. Rhodotorula minuta var. minuta and Rhodotorula minuta var. texensis clearly differed from Rhodotorula glutinis and Rhodotorula rubra in their hexokinase and 6-phosphogluconate dehydrogenase patterns. Rhodotorula marina, Rhodotorula pallida, and Rhodotorula lactosa each had a characteristic pattern. We found three haploid mating type strains to mating type a of Rhodosporidium toruloides, mating type a of Rhodosporidium sphaerocarpum, and mating type α of Rhodosporidium diobovatum among the strains of Rhodotorula glutinis var. rufusa, Rhodotorula glutinis var. salinaria, and Rhodotorula glutinis var. glutinis by performing conjugation tests to confirm the relationships that were revealed when the enzyme patterns were compared. In the genus Rhodosporidium, compatible mating type strains showed similar enzymatic patterns. Strains of Rhodosporidium toruloides which could not assimilate potassium nitrate had the same enzymatic patterns as those that could.