CD30(+)-anaplastic large cell lymphoma (ALCL) is a distinct clinicopathologic entity of non-Hodgkin's lymphoma that is immunologically heterogeneous. Bimodal age distribution, a nonrandom chromosome abnormality [t(2;5)(p23;q35)] that produces a chimeric protein p80npm/alk, and a variable (5-47%) association with Epstein-Barr virus (EBV) have been reported. We reviewed 36 cases of ALCL (19 were children < 20 yr and 17 were adults) by focusing on the presence or absence of p80npm/alk protein and EBV. Immunophenotyping studies were performed on frozen and/or paraffin sections before initiation of chemotherapy. The p80 protein was immunohistochemically examined, and EBV-encoded RNA transcripts were detected by in situ hybridization. Among 19 cases in children, 13 cases had a T-cell and 6 cases had a null-cell phenotype. p80 Was detected in 16 (84.2%) of 19 cases in children and 3 (17.6%) of 17 cases in adults. All of the 19 cases of p80-positive ALCL were positive for epithelial membrane antigen, regardless of age. EBV genome was not detected in any of 19 cases in children and in only 2 of 15 cases in adults. ALCL in childhood seems to constitute a homogeneous entity characterized by expression of p80 and absence of EBV. The association of EBV is also infrequent in adult ALCL among Japanese patients.