Ketoconazole is a new, orally effective, antifungal agent. It is an imidazole compound and like other antifungals of this group, has a wide spectrum of use. Effectiveness has been shown in a variety of deep fungal infections as well as in superficial infections such as candidiasis, dermatophytosis and tinea versicolor. Although it first appeared to be a remarkably safe agent associated with only minor side effects, with more use it has become apparent that symptomatic drug-induced hepatitis occurs in approximately 1 in 12,000 patients. This idiosyncratic side effect and potential effects on testosterone and cortisol synthesis may limit the use of ketoconazole to deep fungal infections and severe recalcitrant superficial infections of the skin.