Autopsy tissues of 19 patients with complications after bone marrow transplantation (BMT) were analysed for the presence of cytomegalovirus (CMV) using histochemical methods. CMV antigens were detected by antibodies to CMV Immediate Early Antigen (IEA) or CMV Late Antigen (LA). CMV-DNA was detected by DNA in situ hybridization (DISH). IEA was detected in one or more tissues in 79% of 14 patients from whom frozen tissue was available. CMV-DNA was detected on paraffin sections in 84% of all 19 patients. CMV components were present in all organs studied; the highest incidence was found in lung, gastrointestinal tract and kidney. In histology, only 37% of patients showed signs of CMV infection by the presence of cytomegalic cells with nuclear inclusions (or so called "owl eye cells"). In tissue culture, only 33% of 15 patients were CMV positive. Serologically, 68% of all patients had active CMV infection, as indicated by a rise in antibody titres. We conclude that the quick detection of CMV IEA and CMV-DNA has a high sensitivity and predictive value, which is comparable to or exceeds the serological detection of CMV.