To evaluate clinical and biologic features of children with non-Hodgkin's lymphoma (NHL) treated in Moscow, Russia, we studied 53 cases treated in the Republican Children's Hospital from 1990 to 1994. Histologic examination disclosed a predominance of the small noncleaved cell subtype (32 cases, 60%); a smaller percentage of the lymphoblastic and large-cell subtypes (14 cases, 26% and 7 cases, 13%, respectively) were identified. The frequencies of primary sites of involvement in descending order included 60% in abdomen, 19% in mediastinum, 15% in head/neck, and 4% in peripheral nodes. The majority of children presented with advanced stage disease (St. Jude stage III/IV/B-ALL, 92.5%). Of interest, 8 of 15 (53%) small noncleaved cell NHL cases examined contained Epstein-Barr virus (EBV). The high frequency of EBV association in this study suggests that this virus may play a more global role in NHL pathogenesis than previously recognized.