Inclusion Criteria:

1. Newly diagnosed or relapsed, de novo or secondary AML
2. First induction chemotherapy cycle
3. Expected neutropenic phase of a minimum duration of 10 days
4. Age >= 18 years
5. Legally signed consent form

Exclusion Criteria:

1. Known proven, probable or possible invasive fungal infection at randomization or in patient history
2. Computed tomography (CT) with any signs of a fungal infection according to the European Organisation for the Research and Treatment of Cancer (EORTC)/Mycosis Study Group (MSG) criteria, i.e. with any infiltrate (Ascioglu, et al 2002)
3. Any current fever unless explained by non-infectious causes
4. Antibacterial prophylaxis other than TMP/SMX
5. Liver function test [LFT] (AST/ALT/bilirubin) more than 3x the upper normal limit

6. Subjects who are receiving and cannot discontinue one of the following drugs at least 24 hours prior to randomization:

   • Drugs with a known possibility of QTc prolongation (e.g. terfenadine, astemizole, cisapride, pimozide, quinidine);
   • Drugs whose plasma levels may be increased by voriconazole therapy (e.g. sulfonylureas, ergot alkaloids, sirolimus, vinca alkaloids).
7. Subjects who have received the following drugs within 14 days prior to randomization: potent inducers of hepatic enzymes that will reduce voriconazole levels (e.g. rifampicin, carbamazepine and barbiturates)
8. Concomitant therapy with absorbable antifungals
9. Patient has a diagnosis of acute hepatitis or cirrhosis due to any cause
10. Known hypersensitivity or other contraindication to voriconazole
11. Patient is unwilling or unable to comply with the protocol.
12. Diseases or disabilities preventing the patient from participating in the trial
13. Females of childbearing potential without negative serum pregnancy test at baseline or within 72 hours prior to start of study drug