Among the clinical isolates hitherto identified as Geotrichum capitatum, two groups were defined from DNA-DNA reassociation experiments. This confirms the existence of two closely related, human-pathogenic Geotrichum species, namely, G. capitatum and G. clavatum. A third group of strains from cactus rots, though morphologically identical to G. capitatum, has a lower moles percent G + C of DNA. The three groups can be recognized by a combination of morphological and physiological characters.