This study will evaluate the efficacy, safety, and toleration of voriconazole compared to conventional therapy with amphotericin B as primary treatment of acute invasive aspergillosis in immunocompromised patients. Although the original protocol allows enrollment of subjects older than 12 years old we do not expect to enroll patients younger than 18 years old. Patients will be randomized to open-labelled therapy with voriconazole or amphotericin B in a one-to-one ratio.