Several methods of cytomegaloviral (CMV) infection diagnosis were studied in patients with a transplanted kidney. EIA was used to examine clinically normal subjects and patients with CMV infection symptoms for the presence of anti-CMV IgM and IgG. Pulmonary cells of the human embryo were infected with the patients' blood and urine, followed by examination for the presence of antigen. After 7 to 14 days part of the infected cultures were examined for virus isolation. The cytological specimens prepared from the saliva and urinary sediment were investigated for the presence of cells containing characteristic CMV inclusions. Altogether 87 patients were examined. Of these, 27 had evident signs of the disease. As for the patients, virus from the blood was isolated in 60, that from the urine in 90% of cases. Viral antigen was found in the cells infected with material from the urine (in 70% of cases) and blood (in 80% of cases). It the group of the clinically normal subjects, the same parameters turned out much lower: virus from the blood was isolated in 12, that from the urine in 11% of cases. In the clinically normal subjects, anti-CMV IgG and IgM were demonstrated in 80 and 21% of cases, respectively. As for the patients, anti-CMV IgG was discovered in 100 and anti-CMV IgM in 70% of cases. All the patients with a transplanted kidney exhibited markers of CMV infection.