Previous studies have detected EBV DNA by Southern blotting or in situ hybridization in biopsy material from up to 30 per cent of adult cases of Hodgkin's disease. Here we have used monoclonal antibodies specific for the EBV latent membrane protein LMP1 to examine archival material from children with Hodgkin's disease. Material from 74 cases (54 males and 20 females) was examined and 37 (30 males and 7 females) were classified as LMP1-positive in the malignant cells. LMP1 positivity was present in 4/13 (31 per cent) of lymphocyte predominant, 14/36 (39 per cent) of nodular sclerosis, 17/20 (85 per cent) of mixed cellularity, 1/2 (50 per cent) of lymphocyte depletion, and 1/3 (33 per cent) of unclassified subtypes. The positive cases by clinical stage were I 9/22 (41 per cent), II 9/20 (45 per cent), III 11/24 (46 per cent), and IV 8/8 (100 per cent). LMP1 positivity was present in 2/5 (40 per cent) children aged less than 5 years, 12/27 (44 per cent) aged 5-10 years, and 23/42 (48 per cent) aged between 10 and 15 years. The association between EBV and Hodgkin's disease in children thus appeared to be more frequent in patients with mixed cellularity and advanced disease, but examples of EBV-positive tumours were found in all histological subtypes, stages, and ages. Stepwise discriminant function analysis showed that clinical stage IV and mixed cellularity histology are independently associated with LMP1 positivity. These observations indicate that Hodgkin's disease in children is at least as strongly linked to EBV as is the disease in adults.