Chemotherapy with alemtuzumab and the combination of cyclophosphamide, adriamycin, oncovin, and prednisone (CHOP) has become experimental trial therapy for aggressive T-cell lymphoma. Several multicenter phase 3 trials will incorporate this scheme. As part of an ongoing phase 2 trial in which we recently treated 20 patients with 8 cycles of CHOP every 2 weeks with 3 additional doses of 30 mg alemtuzumab per cycle, we observed the development of Epstein-Barr virus (EBV)-positive lymphoproliferative disease, after completion of the immunochemotherapy in 3 patients with peripheral T-cell lymphoma. Because the occurrence of EBV-positive lymphoproliferative disease is rare after alemtuzumab monotherapy, such as is given for chronic lymphocytic leukemia, we think that early reporting of this potential side effect is warranted. It may be caused by intrinsic T-cell defects in patients with T-cell lymphoma, or by the combination of alemtuzumab with CHOP chemotherapy.