Infection remains as a major cause of both morbidity and mortality for patients with various types of cancers. The risk of infection increases as new techniques are introduced into medical practice and as greater numbers of patients are treated with more intensive cytotoxic and immunosuppressive therapy. It is therefore essential in the modern practice of oncology that definitive approaches be designed and evaluated to reduce the opportunities for infection. At the Baltimore Cancer Research Center an intensive infection surveillance program assesses the ongoing infectious disease status of the patients and the Center as a whole. From this data base have grown appropriate basic infection control policies and specific research approaches including evaluation of laminar air flow rooms, simpler means of air filtration and reverse isolation, oral nonabsorbable antibiotics and techniques to prevent axillary and oral infections. These programs are enforced by the infection control nurse. A major program has been the reduction of an environmental source of fungi which had contributed to frequent Aspergillus infections. The net result of these varied approaches has been a very substantial reduction in infections among patients at this institution.