Objective: Onychomycosis is a common fungal infection of the nail. This study was aimed to investigate the distribution of dermatophytes isolated from clinical samples of patients with an initial diagnosis of onychomycosis.

Materials and Methods: A total of 882 samples obtained from 822 patients who referred to the Dermatology Clinic of Mustafa Kemal University, School of Medicine between March 2008 and August 2010, with a preliminary diagnosis of onychomycosis were retrospectively evaluated in terms of causative dermatophytes.

Results: Direct microscopy was positive in 60 % of the samples while fungal culture was positive in 15.3 %. Of the isolated dermatophytes, Trichophyton rubrum was identified in 97 % and T. mentagrophytes in 3 %. The presence of dermatophytes was shown in 20.4 % of samples from toenails and in 4 % of samples from fingernails. T. rubrum was identified in 97.6 % of the dermatophytes isolated from the toenail and in 90.9 % from the fingernail.

Conclusion: It was concluded that T. rubrum was the most frequently isolated dermatophyte of both fingernail and toenail onychomycosis.