BACKGROUND: Plantar dermatophytosis frequently goes unnoticed and can cause relapse or re-infestation at other sites. The purpose of this study was to evaluate the incidence of plantar dermatophytosis in association with onyxis and intertrigo involving dermatophytes. PATIENTS AND METHODS: This was a retrospective study in patients seen at mycology consultations between January 2002 and December 2003 and for whom culture revealed dermatophytes on the soles, interdigital spaces and/or toe nails. Gender, age and culture data were record from the laboratory workbooks. RESULTS: 716 patients were included, giving 1291 samples. The sex ratio M/F was 1.5 with a mean age of 48 years. Samples of toe nail were obtained from 591 patients, with plantar samples from 433 patients and intertrigo samples from 267 patients. Plantar dermatophytosis was seen in 66.6% of patients with interdigital-plantar signs, in 75.1% of those with ungual involvement and in 73.9% of cases involving both. T. rubrum was the most frequently isolated dermatophyte. DISCUSSION: Combine involvement of the sole, nail and/or interdigital space was seen in more than 2/3 of cases. Despite the retrospective nature of our study and the evident bias, our results suggest that plantar dermatophytosis is common and should be sought. The sensitivity and specificity of clinical screening methods merit investigation in a prospective study.