The incidence of epidermophytosis of the large folds (ELF) was evaluated in outpatients, the disease course was traced, and the efficiency of sertaconasole therapy was evaluated. The study was carried out within the framework of a multicenter study (2012-2013) in 50 regions of the Russian Federation. A total of 97 therapeutic institutions and 174 physicians partisipated in the study. Authors ’ version of a questionnaire including 27 items was used. A total of 235 questionnaires were processed. The incidence of ELF depended on the gender - men suffered from the disease 1.8 times more often than women. The disease was the most incident (48.1%) in patients aged 35-55years. After 55 years of age, women predominated: they developed the disease 1. 8 times more often. Concomitant diseases of different origin were found in 63.1% patients. Diabetes mellitus predominated (39.6%) and was 1.6 times more incident in women. The mean number of anatomical regions involved in the process was 1.26 ± 0.25. The inguinal (91.5%), gluteal folds(15.7%), folds under the breast (9.8%), axillary (4.7%)folds, and inguinal-scrotal folds in men (4.7%) were involved. The process involved 2-3 large folds in 23.4% patients, symmetrical processes predominated in 61.3%. In case of a unilateral process the physician should remember about fungus carriership and/or asymptomatic course of mycosis. The mycosis was multifocal in 32.8% patients with ELF, with involvement of the soles and with onichomycosis. The most probable etiologicalfactor in these cases was Trichophyton mentagrophytes var. interdigitale. Large folds and soles and nails should be treated in these patients. Sertaconasole (Zalain) proved to be an effective drug for the treatment of ELF, mycosis of soles with onichomycosis with the minimum involvement of the nails. The efficiency of sertaconasole (Zalain) differed significantly in uneventful and complicated process.