Among a series of aminocholesterol derivatives synthesized, 7-aminocholesterol is the strongest inhibitor of yeast cell growth. Using sterol auxotrophic mutant strains, we showed that this compound inhibits cell proliferation by interfering with ergosterol biosynthesis. The sterol pattern of treated cells revealed that 7-aminocholesterol inhibits A 8 ~ A7-sterol isomerase and A14-sterol reductase as morpholine inhibitors. However, the novel feature of this compound is a strong cytotoxicity to yeast.