Although high-dose chemotherapy with autologous peripheral blood stem cell transplantation (autoPBSCT) has been shown or confirmed to be an effective treatment for high-risk and relapsed non-Hodgkin's lymphoma (NHL), relapse after autoPBSCT remains a serious problem. In a clinical trial to overcome relapse, we adopted a treatment plan in which PBSCs purified in vitro to CD34(+) cells to deplete tumor cells (CD34(+) autoPBSCT), total body irradiation (TBI) of 1200 cGy, and melphalan,180 mg/m(2), were used as a preconditioning regimen. Eighteen patients with relapsed or high-risk NHL participated in the study. This study compared the incidence of complications following CD34(+) autoPBSCT preconditioned with the TBI regimen (n = 10): the TBI group; CD34(+) autoPBSCT with the non-TBI regimen (n = 8): the non-TBI group; and unselected autoPBSCT with the non-TBI regimen (n = 19): the unselected autoPBSCT control group. After day 30 posttransplantation, 6 of 10 patients treated with the TBI regimen developed 11 infectious complications in total, compared with only 1 of 8 patients treated with the non-TBI regimen and 4 of 19 patients given unselected autoPBSCT. Two fatal complications occurred in the TBI group, but none occurred in the other 2 groups. The CD4(+) lymphocyte count at 1 month posttransplantation was significantly lower in the TB I group than in the unselected autoPBSCT group. These findings suggest that the addition of TBI to the preconditioning regimen for CD34(+) autoPBSCT is associated with an increased incidence of severe infectious complications after transplantation. (C) 2001 The Japanese Society of Hematology.