Eleven cases of Hodgkin's disease (HD) were examined for the presence of the Epstein-Barr virus (EBV) genome, using the polymerase chain reaction (PCR) to detect EBV DNA in whole paraffin-embedded tissue specimens and in single cells picked out from the specimens with a micromanipulator. The EBV genome was detected in 5 of the 11 cases by conventional PCR. Single cell PCR demonstrated the EBV genome in Reed-Sternberg cells from all the EBV-positive cases, but not from any of the EBV-negative cases. Background lymphocytes and lysozyme-positive histiocytes from EBV-positive cases did not contain the EBV genome. These results indicate an etiological association of EBV with some cases of HD.