The effects of human cytomegalovirus (HCMV) infection on human fibroblast cell genomes were investigated using agarose gel electrophoresis. At selected intervals post-infection (PI), cellular D N A from mock-treated and HCMV-infected cells were prepared in low melting point agarose plugs. Results obtained following electrophoresis of the cellular D N A indicate that HCMV infection did not result in extensive degradation of the cellular DNA, even in samples obtained from cells which showed > 95% cytopathologic effects. High molecular weight DNA (> 23 Kb) comparable to that of the mock-treated samples were noted in a l l HCMV infected DNA samples. Digestion of the DNA samples with restriction endonucleases, EcoR I, Not I, Sfi I, and Nru I, however, resulted in the appearance of smaller DNA fragments (< 23 Kb) in samples obtained on day 3, 4, and 5 PI. Since these DNA bands appeared only in the infected cells, it was likely that these were the HCMV genomic DNA fragments. Findings presented in this study support the notion that the cellular DNA of HCMVinfected cells could remained intact and functiona. KEYWORDS: Cytomegalovirus, chromosomes, DNA, genomes, restriction enzymes