Infections are a frequent complication of patients undergoing cancer chemotherapy. The protected environment - prophylactic antibiotic program has been developed to reduce the risk of infection in these patients. We are evaluating this program in patients with acute leukemia receiving chemotherapy, using a randomized controlled study. In addition, new methods for the diagnosis and treatment of bacterial, fungal, viral and protozoal infections will be developed. Also, new antibacterial, antifungal and antiviral antibiotics will be evaluated for their value in the treatment of infections in cancer patients.