Diseases caused by the normally pathogenic fungi Histoplasma capsulatum, Blastomyces dermatitidis, and Coccidiodes immitis are common but seldom serious. Treatment is usually needed only if respiratory status is compromised, if there is progressive tissue destruction, or if the infection disseminates outside the lungs. The recent availability of ketoconazole has changed the approach to treatment of some forms of fungal disease. Although this drug has no firmly established role, it has proved useful for several aspects of disease. More experience with its use will prove whether it is truly curative or merely suppressive.