Tissues from 22 children with non-Hodgkin lymphoma (NHL) were studied pathologically and immunologically. Most children were noted to have marked (B- or T-cell) neoplasms and the Lukes-Collins classification was predictive of immunologic phenotype in cases where markers were present. Our series and a review of the literature demonstrates that most abdominal NHL are B-cell in origin and are often small noncleaved follicular center cell lymphoma (Burkitt type). Most mediastinal primary lesions are T-cell in origin and of convoluted cell morphology. A few neoplasms (often peripheral nodal) lack the characteristic surface immunoglobulin or erythrocyte rosetting properties of B- or T-cell lesions, respectively. Frequently marrow and central nervous system involvement are observed in T-cell lymphomas and are not in frequent in B cell neoplasms. Shared immunologic and clinical features between the B- or T-cell lymphomas and their leukemic counterparts support the concept that they often differ only in the stage of disease progression.