Polymerase chain reaction (PCR) amplification was used to detect cytomegalovirus (CMV) in tissue culture and in urine specimens from newborns. Synthetic oligonucleotide primer pairs were used to amplify DNA from the major immediate-early and the late antigen genes of CMV. Amplified products were detected by gel electrophoresis and by dot-blot hybridization with oligonucleotide probes. Using one or both of the primer pairs and associated probes, we found 46 different tissue culture isolates of CMV that were positive; no reaction products were detected when the same primers and probes were used to amplify other herpes family viruses or human genomic DNA. Urine samples from 44 congenitally infected infants were positive when tested with one or both primer pairs and probes. When compared with tissue culture, detection by gel electrophoresis provided a sensitivity of 93%, a specificity of 100%, and a predictive value of a positive result of 100%. Dot-blot analysis raised the sensitivity to 100%. We conclude that PCR amplification may be a valuable tool for diagnosing congenital CMV infection.