OBJECTIVE: To establish whether polymerase chain reaction (PCR) for cytomegalovirus deoxyribonucleic acid (DNA) can provide clinical information for the management of the infection. METHODS: Leukocytes in 30 heart transplant recipients were monitored by pp65 antigen testing and PCR for 82 to 365 days after transplantation. RESULTS: Of the 30 patients, 26 developed cytomegalovirus infection, nine of whom were symptomatic. Altogether, 300 leukocyte samples were examined. The concordance between PCR and pp65 antigen test was 82.6%. In symptomatic patients after surgery, PCR detected cytomegalovirus infection after 38 plus minus 16 days and the pp65 antigen test, after 48 plus minus 15 days. Symptomatic infection correlated with a higher number of pp65-positive leukocytes than did asymptomatic infection: 310 plus minus 356 vs 24 plus minus 35 (p < 0.005)/200,000 examined, respectively. Clearance of virus was observed by PCR after 125 plus minus 73 days (range 29 to 225) in symptomatic, and after 82 plus minus 70 days (range 16 to 301) in asymptomatic, cases of infection. CONCLUSIONS: The positive predictive value of PCR for symptomatic infection was 34.6%. Our findings correlate with previous reports and show that the qualitative detection of cytomegalovirus DNA is not associated with overt disease whereas quantitation of pp65-positive leukocytes closely correlate with symptom onset. Insofar as the results are not quantitative, PCR is not a marker of clinically apparent infection. Careful monitoring of cytomegalovirus infection based on quantitative pp65 antigen assay can fulfill all clinical needs for early diagnosis and proper management of the infection