The search for antifungal drugs, particularly oral agents with a broad spectrum of activity, led to the study of itraconazole, a triazole. In vitro susceptibility testing suggested activity against a variety of fungal pathogens affecting humans. Pharmacokinetic studies indicated absorption after oral administration to patients, with prolonged serum concentrations and peak levels exceeding the in vitro inhibitory concentrations for most pathogens. Twenty-four patients have been enrolled in efficacy studies; two-thirds of these individuals had experienced a relapse after apparently successful therapy with other drugs, had failed to respond to other drug therapy, and/or had experienced intolerable side effects with other drugs. Fourteen patients have thus far responded to treatment with itraconazole; this group includes two persons each with coccidioidal pneumonia and adenopathy, pulmonary coccidioidomycosis, and dermatophytosis plus onychomycosis as well as one person each with coccidioidal epididymitis, adrenal histoplasmosis, head and neck histoplasmosis, cutaneous blastomycosis, oral-sinonasal alternariosis, chromoblastomycosis, invasive pulmonary aspergillosis with fungus ball, and onychomycosis. Five other patients have had partial responses to therapy, three have failed to respond, and two have been deemed unassessable. Drug toxicity has been limited in 211.8 patientmonths of therapy. The results are encouraging and indicate that more extensive studies are warranted.