A previously described Candida albicans nystatin resistant mutant blocked in 14 alpha-demethylation of lanosterol was shown to also lack all traces of cytochrome P450 as determined by carbon monoxide difference spectra. This strain does not require ergosterol for growth and reverted to an ergosterol producing, cytochrome P450 containing strain indicating no other lesions. Cytochrome P450 mutants described in Saccharomyces cerevisiae are auxotrophic for ergosterol or contain a second mutation in 5,6 desaturation of the sterol B ring. These results suggest that a cytochrome P450 lesion in these yeasts have different phenotypes and may reflect different sterol requirements for the two organisms.