The antifungal activity of posaconazole (SCH56592), a new triazole antifungal, against stock cultures and fresh clinical isolates of a wide range of pathogenic fungi was compared with that of itraconazole, fluconazole and amphotericin B. Posaconazole inhibited growth of all the fungal species tested except Fusarium spp. at 1 mg/l or lower concentrations, showing a broad-spectrum antifungal activity. The activities of posaconazole for all the fungal species far surpassed those of fluconazole and were even superior to those of itraconazole for Aspergillus spp. as well as for many other fungal species.