Morbidity and mortality in patients with malignancies, especially leukemia and lymphoma, are increased by invasive fungal infections. Since diagnosis of invasive fungal infection is often delayed, antifungal prophylaxis is an attractive approach for patients expecting prolonged neutropenia. Antifungal prophylaxis has obviously attracted much interest resulting in dozens of clinical trials since the late 1970s. The non-absorbable polyenes are probably ineffective in preventing invasive fungal infections, but may reduce superficial mycoses. Intravenous amphotericin B and the newer azoles were used in clinical trials, but their role in antifungal prophylaxis is still not well defined. Allogeneic stem cell transplant recipients are at particularly high risk for invasive fungal infections. Other well described risk factors are neutropenia >10 days, corticosteroid therapy, sustained immunosuppression, graft versus host disease, and concomitant viral infections. The enormous study efforts are contrasted by a scarcity of risk stratified evidence based recommendations for clinical decision making. The objective of this review accumulating information on about 10.000 patients is to assess evidence based criteria primarily regarding the efficacy of antifungal prophylaxis in neutropenic cancer patients.