Chemoradiotherapy-induced toxicity following unmodified allogeneic marrow grafting was studied. Patients with hematologic malignancy (n = 157) received cyclophosphamide (120 mg/kg) followed by single or fractionated total body irradiation (TBI); aplastic anemia patients (n = 41) received only cyclophosphamide (200 mg/kg). Physicians rated mucositis, pain and nausea daily as (0) none, (1) mild, (2) moderate, (3) severe, (4) life threatening. Oral mucositis pain began several days prior to transplant, peaked during the second week after transplant, and declined thereafter. Patients with hematologic malignancies (maximum mean rating of 1.6, day 11) experienced more pain than aplastic anemia patients (maximum mean rating of 0.7, day 6). Nausea peaked before transplant and gradually declined. Nausea was higher (p less than 0.001) in patients with aplastic anemia (maximum mean rating of 1.3, day -2) than with hematologic malignancies (maximum mean rating of 0.9, day -6). There was no significant difference between single dose 1000 cGy and 6-day 1200 cGy irradiation. Recipients of 1575 cGy rather than 1200 cGy TBI had significantly (p less than 0.01) higher levels of pain (mean rating 1.25 and 0.82, respectively) and nausea (mean rating 1.27 and 0.72, respectively). Additional research is needed to determine the predictors, consequences and best methods of controlling these toxicities.