Epstein--Barr virus (EBV) is associated with Hodgkin's disease (HD). However, EBV-positive Reed--Sternberg (RS) cells and EBV-positive B lymphocytes co-exist in the same EBV-positive lymph node affected by HD. In a previous report, using total lymph node DNA, the presence of two distinct EBV strains was demonstrated, but their cellular localization (i.e. RS cells vs B lymphocytes) could not be determined. To address this question, three patients with EBV-associated HD were selected in the present study and single-cell PCR of the latent membrane protein-1 (LMP-1) gene from isolated RS cells was performed. In one case, it was clear that RS cells and B lymphocytes were infected by different EBV strains. In the two remaining cases, only one band was detected from total lymph node DNA. However, single-cell PCR showed that RS cells in each sample were infected by single EBV strains, which were different from those detected in lymphoblastoid cell lines derived from EBV-positive B lymphocytes of lymph node cell suspensions from these two patients.