A 10-year-old boy with chronic active Epstein-Barr virus (EBV) infection developed T-cell lymphoproliferation in the terminal stage of hepatic failure. The phenotypes of the proliferating lymphocytes were CD3+, CD4+ and HLA-DR+. The genomic DNAs from these cells demonstrated two rearranged T-cell receptor beta-chain genes and contained the EBV genome. These findings indicate that EBV can infect T lymphocytes and might cause clonal T-cell lymphoproliferation.