The objective of this study is to evaluate the efficacy, safety and toleration of voriconazole in the primary treatment of systemic or invasive fungal infections due to fungal pathogens for which there is no licensed therapy; and in the secondary treatment of systemic or invasive fungal infections in patients failing or intolerant to treatment with approved systemic antifungal agents. This trial is a Phase III multicenter, open label study investigating the utilization of voriconazole for the treatment of systemic or invasive fungal infections. Enrollment is targeted for 150 patients to be recruited from multiple centers. The patient population will consist of patients with proven, deeply invasive fungal infection for which there is no licensed therapy or if the patient is failing or intolerant to treatment with approved systemic antifungal agents. Voriconazole will be administered initially by a loading dose of 6 mg/kg q12 hours for the first two doses followed by 4 mg/kg q12 hours. Efficacy will be evaluated by clinical, radiological and microbiological response.