Background: INFECTIONS caused by opportunistic yeasts such as CANDIDA species, Trichosporon, Rhodotorula and Saccharomyces have increased in immunocompromised patients and their identification is crucial as intrinsic and acquired resistance of some yeast species to antifungal agents are on the rise. The aim of this study was to identify the organisms to the species level in order to suggest accurate and effective antifungal therapies.Methods: In this study that carried out in Tehran, Iran in 2009, 200 patients with yeast infection were medically examined and clinical specimens were prepared for direct examination and culture on Sabouraud dextrose agar. Subsequently, the isolated yeast colonies were identified using various tests including culture on Corn Meal agar with Tween 80, CHROMagar CANDIDA and casein agar. For the definite identification of organisms some biochemical tests were done based on carbohydrate assimilation by RapID Yeast Plus System kit, and, finally, a molecular method, PCR-RFLP, using Hpa II enzyme, was performed for the remaining unknown yeast species.Results: A total of 211 yeast isolates were identified in 200 patients with yeast INFECTIONS. The most frequent isolated yeasts were CANDIDA albicans, 124 (58.77%), followed by CANDIDA parapsilosis, 36 (17.06%), CANDIDA tropicalis, 17 (8.06%), CANDIDA glabrata, 13 (6.16%), CANDIDA krusei, 8 (3.79%), CANDIDA guilliermondii, 2 (0.96%), Trichosporon, 3 (1.14%), Rhodotorula, 1 (0.47%), Saccaromyces cerevisiae, 1 (0.47%) and other yeast species, 6 (2.84%).Conclusion: Nail candidiasis was the most prevalent type of yeast infection in the patients and CANDIDA albicans was the most frequent isolated species from all clinical specimens.