A double-blind study comparing the antifungal efficacy of systemic ketoconazole in twenty volunteers who had pityriasis versicolor (mycologically proved) was done. Ketoconazole cured 90% of all volunteers taking the drug at the end of the 4-week follow-up, even though they were all treated for only 2 weeks. Of placebo-treated volunteers, 20% were cured of their disease. No adverse reactions were noted.