Intruduction. A long course of onychomycosis, severe hyperkeratosis, slow growth of the nails of the feet, somatic burden, as well as an increase in the resistance of pathogens often lead to a decrease in the effectiveness of traditional antimycotics, dictating the need to create new methods of therapy. A promising direction of treatment is the use of alternating current of supratonal frequency of high voltage and low power — ultratonotherapy (UT) in combination with antifungal drugs. The article presents data on the mechanisms of action and clinical effectiveness of this method in the complex treatment of foot onychomycosis. Aim of study — to study the mechanisms of action and evaluate the clinical effectiveness of UT in the complex treatment of foot onychomycosis. Material and methods. The antifungal effect of UT was studied in the colonies of Trichophyton rubrum and Candida albicans. The distribution of ozone released during the procedure on the affected nail plate was evaluated in vitro using a qualitative chemical reaction and photodermatoscopy. The state of tissue blood flow in the periungual tissues under the influence of UT was studied in vivo by means of ultrasound dopplerographic scanning (USDGS). The clinical effectiveness of the method was evaluated according to the results of complex treatment of patients with foot onychomycosis in comparison with traditional methods of therapy. Results. UT has both fungicidal and fungistatic effects. With a qualitative reaction to ozone, coloring of the surface and small structures of the nail plate was noted. According to the USDGS, after the use of UT, a significant increase in blood supply to the periungual tissues was recorded. The combined use of alternating current of a high voltage ultrasonic frequency with antifungal drugs in patients with foot onychomycosis contributes to the rapid growth of the nail and shorten the duration of mycological cure. Conclusion. UT has an antifungal effect and improves microcirculation in the area of the nail bed. In the complex treatment of patients with foot onychomycosis, the method accelerates clinical and mycological cure, stimulates nail growth, which reduces the rate of systemic and local antifungal therapy.