Onychomycosis is a group of the most common infectious nail diseases of fungal etiology. According to various authors, onychomycosis affects up to 20% of the population. Trichophyton rubrum is the main causative agent (80%) of toenail onychomycosis. Preventive measures are important for treatment success and prevention of onychomycosis recurrence. Treatment of shoes is an important comopnent of preventive measures. Material and methods. The article presents the results of clinical studies of the efficacy of a Timson device for antifungal treatment of shoes (insoles). Thirty-five experiments were performed. The Tr. rubrum test cultures previously grown on Sabouraud agar medium were used. The batches of the cultures were grown in an incubator at t=28 °C for 14 days prior to start of the study. At the end of the incubation period, the presence of Trichophytonrubrum colonies was assessed in control Petri dishes and in the dishes after the insoles had been treated using the Timson device. Results and Conclusions. A high efficiency of the method (94.3%) was revealed. In two experiments in which the growth of Tr.rubrum culture was observed even after the treatment, the number of colonies decreased abruptly compared to the control.