Cytomegalovirus (CMV) infectious titers and DNA levels were determined by quantitative shell vial culture and quantitative-competitive PCR with blood samples from 10 renal transplant recipients with active CMV infection. Blood samples were stored at either room temperature or 4°C and were processed at intervals of 0, 6, 24, 48, and 72 h. All samples were culture and PCR positive at baseline. Whereas the sensitivity of shell vial culture progressively declined, with only 55% positive at 24 h and 10% positive at 48 h, all samples remained PCR positive at all time points. Furthermore, the infectious titer diminished by 83 to 91% by 24 h compared to that at baseline (P < 0.0001), but quantitative DNA levels did not decline over time. Storage temperature had no significant effect on either infectious titer or DNA levels.