Each of seven pathogenic species of Candida exhibits a unique pattern of light and dark recovery responses to ultraviolet irradiation. C. guiliermondii, C. parapsilosis and C. pseudotropicalis photoreactivate whereas C. albicans, C. krusei, C. stellatoidea and C. tropicalis do not. Within each of these groups, individual species are distinguishable by whether or not they express differential dark recovery during postirradiation growth at 25 C or 37 C on oxidative vs fermentative carbon sources, on inorganic vs amino acid nitrogen sources or in the presence rather than absence of ergosterol. Equivalent recovery patterns are obtained for species of Candida and the ascosporogenous species which are their corresponding perfect forms. These observations indicate strongly that the post-irradation recovery is a reliable, species-specific characteristic of yeasts.