An investigative study was performed to determine the diagnosis of onychomycosis in a South Florida geriatric population. In this study, 450 cases of suspected onychomycosis involving men and women 65 years of age and older from a private practice office and two nursing home settings were used. Samples were taken from the hallux toenail and sent to a mycology laboratory for fluorescent potassium hydroxide (KOH) preparation and microscopic examination of a fungal culture. Of the 450 cases studied, 46.4% of the patients had a single fungal organism cultured, 30.4% had a mixed fungal infection cultured, and 23.1% had no fungal growth. Saprophytes were found in 59.9% of the 526 total fungal organisms cultured while dermatophytes were found in only 23.8%. The results of this investigation demonstrate that there may be a shift from isolated dermatophyte infection to mixed saprophyte infections in a geriatric population with onychomycosis.