Thirty renal transplant recipients, after transplantation, were tested weekly with the following assays: cytomegalovirus (CMV) antigenemia (pp65 Ag), plasma qualitative Amplicor CMV (P-AMP), plasma and peripheral blood leukocyte quantitative Amplicor CMV monitor (P- and PBL-CMM), peripheral blood leukocyte (PBL) quantitative Quantiplex bDNA CMV, version 2.0 (bDNA), and whole-blood Nuclisens pp67 CMV (pp67). Eleven patients developed symptomatic CMV disease, and 7 developed asymptomatic CMV infection. For prediction of CMV disease, the sensitivity, specificity, and positive and negative predictive values, respectively, were as follows: 100%, 63%, 61%, and 100% for pp65 Ag; 100%, 42%, 50%, and 100% for bDNA; 91%, 47%, 50%, and 90% for PBL-CMM; 55%, 74%, 55%, and 74% for P-AMP; 55%, 74%, 55%, and 74% for P-CMM; and 64%, 79%, 64%, and 79% for pp67. First positive results in PBL were obtained 9-10 days before symptoms of CMV disease, compared with 5-6 days in plasma and 0 days in whole blood. PBL assays appear to be more appropriate than plasma assays when pre-emptive therapy is required to prevent the rapid progression from the first detection of the virus to CMV disease.