We report a pulmonary angiocentric immunoproliferative lesion (AIL) in an 11-year-old boy with chronic active Epstein-Barr virus (EBV) infection. The phenotypes of the proliferating lymphoid cells in the biopsied pulmonary lesion were CD2+, CD3+, CD4+, CD5+, CD7+, and HLA-DR+. EBV DNA was detected in the tumorous and the nontumorous tissue by Southern-blotting studies. Dual immunostains and combined immunohistochemistry/in situ hybridization showed the simultaneous presence of EBV-determined nuclear antigen or EBV-encoded small RNAs and T-cell markers in the lymphoid cells. Molecular genetic analysis of the tumorous lesion diagnosed as AIL grade III showed no clonal rearrangement of the T-cell receptor beta gene but a single type of fused terminal band of EBV. No such evidence of monoclonality was identified in the surrounding nontumorous tissue diagnosed as AIL grade I or II. The present case was a rare example of AIL in childhood and provides further histopathologic and molecular biological evidence supporting the concept of AIL as a continuous spectrum from premalignant lymphoproliferative disorders to monoclonal, overt malignant lymphoma.