Some clinical manifestations following exchange transfusion (ET) could result from graft versus host disease secondary to the introduction of viable foreign T lymphocytes: skin rash, fever, acute and sometimes bloody diarrhea or enterocolitis. Between February 1985 and January 1989 the blood used for 31 ET was irradiated at 40 grays. We compared the manifestations occurring during the days following ET to those occurring after 44 previous ET with non irradiated blood during the period January 1981 to January 1985. From 1981 to 1985, 13 of 44 infants developed problems within 3 days following ET: an erythematous macular skin rash in 4; gastrointestinal manifestations (diarrhea, vomiting and rectal bleeding, necrotizing enterocolitis) in 7; both skin lesions and a gastrointestinal problem in 2. Since 1985, 27 infants had no problems whereas only 4 developed gastrointestinal or cutaneous manifestations: NEC in a preterm infant, abdominal distension with rectal bleeding, fever and petechial rash in 2 infected infants. These data show a dramatic decrease of complications since the irradiation of blood products has been started: 30% with non irradiated, 13% with irradiated blood.