Twenty three patients with culture positive onychomycosis were treated topically twice daily for 2-6 month with a solution containing 10 g urea, 15 g lactic acid, 4 g NaOH, 21 g water, and 50 g propylene glycol. Trichophyton rubrum was cultured in 17 patients and Candida albicans in 6 patients. The solution was effective in 21 of the 23 patients with cure in 2 patients, marked improvement in 11 patients and improvement in 8 of the patients. In the patients with marked improvement some nails were often completely cured. The good effect of this solution in the treatment of onychomycosis is in correlation with a good in vitro activity with MICs of 5% against Tr. rubrum and 10% against C. albicans and a high penetration into nails in vitro. The patients found the solution cosmetically attractive and no side effects were noticed by the patients. Even if the treatment period was short the good effect in the majority of the patients indicates that this solution is effective in topical treatment of onychomycosis.