High molecular weight human cytomegalovirus (CMV) DNA was isolated from agarose-embedded infected human diploid cells by employing field inversion gel electrophoresis. A high yield of CMV DNA molecules was obtained within 1 week of infecting the cell culture. Labelling of the viral DNA with biotin by nick translation enabled the detection of CMV-infected cells in sections of paraffin-embedded human adrenal gland by in situ hybridizatio