A new oral triazole antifungal, SCH 39304, was administered to 54 patients with progressive infections due to Coccidioides immitis from six collaborating centers. Patients were grouped according to site of infection including chronic pulmonary (25), bone/joint (17) and skin/soft tissue (12). The median age was 40 years; 83% were male, 52% white, 13% HIV-infected and 35% had failed previous therapy. The majority of patients were treated with either 100 mg or 200 mg day-1. One patient on renal dialysis received 300 mg day-1. Baseline abnormalities were reassessed for evidence of efficacy every 4 months and expressed in a standardized scoring system. Cumulative overall response rates at 4, 8 and 12 months were 7%, 36% and 66% respectively. Twelve month response rates by disease were 77% (pulmonary), 62% (skin/soft tissue) and 31% (bone/joint). Fifteen patients failed therapy although seven of these were still on treatment when the study was discontinued. Two failed due to toxicity. Possible symptoms or signs of toxicity occurred in 24 (44%) patients and were generally mild. SCH 39304 is an effective and well tolerated therapy for progressive forms of coccidioidomycosis.