The dimorphic yeast Candida albicans, as a member of the fungi imperfecti, has been assumed to be in the haploid, or imperfect, state. The deoxyribonucleic acid content of this species has been measured by flow microfluorometry, a technique capable of analyzing single cells. These results were compared with flow microfluorometric deoxyribonucleic acid determinations on a series of strains of Saccharomyces cerevisiae of known ploidy (haploid, diploid, triploid, and tetraploid). These ploidy levels were readily distinguished by the flow microfluorometry procedure. By this criterion, C. albicans was found to contain a diploid amount of deoxyribonucleic acid. Ultraviolet radiation survival and chemical mutagenesis experiments support the conclusion that both clinically isolated and laboratory strains of C. albicans are diploid.