The imidazole derivative ketoconazole is approved in the Netherlands for treatment of local and systemic fungal infections. Despite the risk of major hepatic damage, this antimycotic drug is still being used in daily practice for the oral treatment of patients with onychomycosis. Since April 1986, 18 cases of relatively severe hepatic damage in the Netherlands were ascribed to the oral use of ketoconazole for the treatment of onychomycosis, skin infection or vaginal candidiasis. Given the potential risk for the patients concerned, ketoconazole should no longer be prescribed for relatively mild cosmetic disorders such as onychomycosis.