Porcine cytomegalovirus (PCMV) is an undesired pathogen in pigs intended for use as organ donors in xenotransplantation. In the present work, we characterized the first set of genes of PCMV. From a German isolate, the DNA polymerase (DPOL) locus was amplified and two complete open reading frames (ORF) as well as two partial ORFs including the complete DPOL gene and the 3'-end of the glycoprotein gB gene were sequenced. The deduced amino acid sequences showed the highest identities with the respective proteins of the betaherpesviruses, in particular those (ORFs 36-39) of the human herpesviruses 6 and 7 (HHV-6 and -7). In phylogenetic analysis, PCMV clustered also with HHV-6 and HHV-7. On this basis, PCMV could be firmly classified to the Betaherpesvirinae and tentatively assigned to the genus Roseolovirus. In addition to the German isolate, the DPOL gene was analysed from a British and a Japanese strain as well as a Spanish isolate. Differences of 0.4 to 1% were found on the nucleotide and the amino acid level. On the basis of the conserved regions, primer pairs were selected for PCR which detected PCMV in blood and tissue samples from four European countries. Therefore, these are the first nucleic acid-based test systems which were shown to universally detect PCMV. The application of these assays to organs of domestic pigs from Germany revealed a PCMV prevalence of > 50%.