Intravenous cytomegalovirus (CMV) hyperimmune globulin therapy was used in 24 episodes of proven CMV disease in 22 renal allograft recipients. All patients had fever up to 39-40 degrees C for at least 3 days. Many patients had thrombocytopenia, leukopenia, and/or elevation of serum transaminase levels. Five had pneumonitis. The diagnosis of CMV infection was confirmed by isolation of virus from urine or bronchoalveolar lavage fluid using a rapid culture method based on the demonstration of CMV early nuclear protein in cell culture monolayers and/or by the demonstration of CMV specific IgM antibodies. The hyperimmune globulin was given until fever disappeared. The infusions were well tolerated and no side effects were recorded. A clinical response defined as normalization of body temperature, occurred in 23/24 cases. One patient with septic fever and a fatal outcome had a superinfection with tuberculosis. Two other fatal complications were caused by invasive pulmonary aspergillosis and by multiple penetrating duodenal ulcers. Two reversible acute rejections and one recurrence of the original renal disease were recorded. 19/22 patients are alive, 18 with normal renal function. We conclude that hyperimmune globulin therapy is well tolerated and may help to control sever CMV infections in renal transplant recipients.