From April 1988 to March 1991 28 children with generalized solid tumors (N = 15) or hematologic malignancies (N = 13) received intensified myelotoxic regimens followed by autologous stem cell rescue (ABMT). These intensified regimens consisted of 12 Gy fractionated total body irradiation (FTBI) and 2 (or 3) cytotoxic drugs (group A, n = 19) or a combination of 3 cytotoxic drugs (group B, n = 9). FTBI-containing regimens produced more severe mucositis > = WHO grade 3 (p = 0.01) and a longer duration of severe mucositis. The mucositis had a median duration of 8 days (range 0-28) in group A compared with median 0 days (range 0-7) in group B (p < 0.01). Acute renal and liver toxicity were not different. The probability of overall survival at day +100 was 89% in all patients. In terms of long-term survival FTBI containing regimen did not prove superior: 5 out of 19 patients in group A and 6 out of 9 patients in group B have been survivors for a minimum of 3 years. In conclusion, severe gastrointestinal toxicity of such intensive regimens is avoidable if FTBI is omitted.