To evaluate the efficacy and safety of voriconazole in acute invasive aspergillosis (IA), an open, noncomparative multicenter study was conducted. Immunocompromised patients with IA were treated with intravenously administered voriconazole 6 mg/kg twice a day (b.i.d.) twice and then 3 mg/kg b.i.d. for 6-27 days, followed by 200 mg b.i.d. administered orally for up to 24 weeks. Response was assessed by clinical and radiographic change. A total of 116 patients were assessable. IA was proven in 48 (41%) and probable in 68 patients. Voriconazole was given as primary therapy in 60 (52%). Good responses were seen in 56 (48%); 16 (14%) showed complete response and 40 (34%) partial response. A stable response was seen in 24 patients (21%), and 36 (31%) of the infections failed to respond to therapy. Good responses were seen in 60% of those with pulmonary or tracheobronchial IA (n=84), 16% with cerebral IA (n=19), 58% with hematologic disorders (n=67), and 26% of allogeneic stem cell transplant recipients (n=23). Voriconazole is efficacious in treating acute IA.