Ozonized sunflower oil, Oleozon, has a remarkable gerrmicidal action. In the present study, the efficacy of Oleozon in the treatment of tinea pedis was demonstrated in a controlled randomized phase III assay, comparing topical Oleozon with ketoconazole cream 2% (Nizoral) in 200 patients (100 in each group). The treatment administered was twice per day for a period of 6 weeks. The efficacy was evaluated clinically (disappearance of all lesions, with or without negative mycological results) and mycologically (negative culture results). A complete clinical and mycological cure was obtained in 75 and 81% for Oleozon and ketoconazole, respectively, with no significant differences between both groups. No side-effects or bacterial super-infections were observed. Patients were evaluated 6 months after the end of the treatment and no recurrence was observed in the Oleozon group. Oleozon can be an effective alternative low-cost antimycotic drug.