The presence of Epstein-Barr virus (EBV) DNA in formalin-fixed, paraffin-embedded samples of Hodgkin's disease (HD) was investigated by Southern blot hybridization using a specific EBV Bam H1W fragment probe. DNA from 16 samples of HD in children and young adults was compared with that from ten samples in adults older than 45 years. A further eight cases of DNA extracted from fresh samples of HD were also studied, in order to compare the results obtained with fresh and fixed tissue samples. Hybridization was demonstrated in 15 of the 34 cases of HD studied in contrast to 3 or the 34 control specimens of non-Hodgkin's lymphoma, non-neoplastic lymph nodes, and carcinomas. No differences between the two age groups compared were found. The results of this study suggest that there is a definite association between EBV and HD, although the exact nature of this association remains to be established. It has also been shown that DNA of sufficient quality for the detection of EBV DNA can be extracted from formalin-fixed, paraffin-embedded material, and that comparable results can be obtained using DNA extracted from fresh and fixed tissue.