This study presents the epidemiological and mycological aspects of 299 patients with nail lesions who were referred to three diagnostic laboratories in the city of Cali. The diagnosis of mycoses was established through visualization of mycotic structures in a direct microscopic examination of skin scrapings and by isolation. Onychomycosis was found in 183 cases (61.2%), of which 141 were in toenails (44 in males and 97 in females), 38 in fingernails (9 males and 29 females), and 4 cases in toenails and fingernails simultaneously (all females). No statistically significant relation was found between sex and onychomycosis. Yeasts accounted for 40.7% of the mycoses, dermatophytes for 38%, nondermatophyte molds for 14% and the etiology was mixed in the remaining cases (7.3%). Candida albicans was the most commonly isolated yeast species; the most common dermatophyte was Trichophyton rubrum and Fusarium spp. and Scytalidium dimidiatum were the most common nondermatophytic molds. Them common fungi found in fingernails were yeasts; in toenails dermatophytes were more prevalent (chi2 with Yates' correction = 19.75, P= 0.000088). Yeasts were observed more frequently in females while dermatophytes were more common in males. The difference between these two etiologic groups was statistically significant (chi2 with Yates' correction = 7.43, P = 0.0064); no relation was observed according to age.