A rapid and simple application of the polymerase chain reaction is described for the detection of human cytomegalovirus (HCMV) mRNAs in cells infected in-vitro. The method was first used to study the transcription of two HCMV genes, and confirm the link between the transcription of one, encoding for the major capsid protein, and viral replication. The oligonucleotides chosen in this region were specific for HCMV genome and sensitivity experiments showed that a single infected cell in 5 x 10(5) can be detected. Detection of this transcript should be suitable for diagnostic purposes, permitting the distinction between latency and active infection.