The clinical and histopathological findings in 26 children with non-Hodgkin's lymphoma without initial marrow involvement are reviewed. A marked male predominance similar to that observed in previous series was noted. Biopsy material was classified according to the recommendations of Rappaport in 22 cases. All have diffuse lymphomas, and 16 of 22 patients had diffuse, poorly-differentiated, lymphocytic lymphoma. Twelve of 26 patients had involvement of the mediastinum as part of their initial presentation. Of these 12, 5 developed lymphomatous involvement of the central nervous system prior to the development of leukemic transformation of the bone marrow. This observation suggests that prophylactic therapy against CNS relapse be considered for children with mediastinal non-Hodgkin's lymphoma, even in the absence of initial marrow involvement.