Epidemiologic studies have implicated Epstein-Barr virus (EBV) in the great majority (80%-100%) of Hodgkin disease (HD) cases in South American countries, versus only 30%-40% in the United States and other industrialized countries. Other EBV-related malignancies are known to be geographically localized, including nasopharyngeal carcinoma in south China and Burkitt lymphoma in equatorial Africa. Some studies, however, have suggested that age and histiotype, rather than geographic region, are the major determinants of the association between EBV and HD. To further characterize this relationship in children, we matched 26 cases of pediatric Hodgkin disease from south Brazil and 26 cases from the U.S.-forhistiotype and age. The Brazilian children (22 males, 4 females) had a median age of 9 years, while the median age of the U.S. group (11 males, 15 females) was 7.5 years. Formalin-fixed, paraffin-embedded biopsy material was examined for EBV early RNA1 (EBER1) expression by in situ hybridization. This antigen was detected solely in Reed-Sternberg cells or their variants in positive samples. The same proportion of cases was positive (15/26 or 58%) in both groups of children. After adjustment for histiotype and age, the association between EBV and HD remained independent of geographic location, but was more frequent in children aged < or = 10 years at diagnosis. These findings support the multiple-etiology hypothesis for Hodgkin disease.