An anti-human cytomegalovirus (HCMV) antibody in 330 sera from patients and normal subjects was examined by ELISA. The test results were compared with the results of CF test and there was 99.1% agreement. Specific anti-HCMV IgM antibody was searched for and only 4 sera were positive. This makes it unlikely that screening for IgM anti-HCMV will effectively prevent posttransfusion HCMV infections.