The Epstein-Barr virus (EBV) has been consistently found to be associated with Hodgkin's disease (HD) in two ways: cases generally have elevated titer distributions of antibodies against the viral capsid antigen, and the occurrence of HD among persons with a history of EBV infectious mononucleosis is two or three times higher than expected. We evaluated this association by measuring the prevalence and level of antibodies against EBV and related viruses among 304 cases of HD interviewed in a population-based study in comparison to 285 of their siblings. The most significant finding was that antibody titers to the viral capsid antigen of EBV were elevated (± 1:320) in 39% of the cases and in only 14% of the sibling-controls; the relative risk adjusted for age and sex was 4.1. The geometric mean titer was three-fold higher among cases (175.6vs. 58.1) Subjects who reported a history of IM had a higher distribution of titers than those who did not. Cases also had elevated titers against the early antigen of EBV - the D Component being most prominent. A significantly higher proportion of cases has elevated titers against CMV, relative risk = 3.4, but the prevalence of CMV antibody was relatively low and not consistently higher among cases. The findings support the hypothesis that EBV may play a role in the pathogenesis of HD among persons with elevated titers. The findings neither confirm nor deny a possible role of CMV.