Oral geotrichosis is an uncommon opportunistic infection caused by Geotrichum candidum, a habitual contaminant and component of the flora of various parts of the body. This communication reports both a 20-year retrospective study of clinically and mycologically proven cases of oral geotrichosis, and a prospective study of fungal oral flora in 200 individuals divided into two groups: normal individuals and individuals with associated conditions. Twelve patients with proven oral geotrichosis were included: 9 females and 3 males, with a mean age of 48.5 years; the associated conditions were diabetes mellitus (66.6%), leukemia, Hodgkin's lymphoma and HIV/AIDS infection. The oral geotrichoses showed three clinical varieties: pseudomembranous (75%), hyperplastic, and palatine ulcer. G. candidum was isolated in 11 cases and G. capitatum in one. Positive fungal cultures were obtained from the two groups, and 48% and 78% of cultures were positive, respectively, for Candida spp. In 2.8% and 6.33% of the cases, G. candidum was isolated, respectively, together with one strain of G. capitatum. Oral geotrichosis is an exceptional infection that clinically presents, and is treated, as oral candidiasis. G. candidum may be isolated from the oral flora of a small proportion of patients, either normal individuals or those with associated conditions. (J Oral Sci 52, 477-483, 2010)