Despite dramatic improvements in patient and renal allograft survival, infections continue to be an important cause of post-transplantation morbidity and mortality. Most serious infections manifest clinically as febrile diseases, and immunosuppression-induced compromised cell-mediated immunity is the basis for the predominance of infections due to opportunistic intracellular microorganisms. Diagnostic evaluation is guided by the timing of fever after transplantation, epidemiologic factors, and evidence of specific organ system involvement. Although current therapy of bacterial and parasitic infections is usually effective, the management of deep-seated fungal infections remains highly unsatisfactory. Cytomegalovirus disease, the single most important infection in some transplant centers, frequently presents as a self-limited viral syndrome; however, multiple organs may be affected. New measures for the rapid diagnosis and treatment of this viral infection hold promise. A number of recommendations have been proposed to prevent infections in renal transplant recipients; however, continued progress will depend primarily upon further refinements in immunosuppressive therapy.