A chemotherapy regimen based on high doses of BCNU and mitomycin C with autologous bone marrow transplantation was used in 18 patients with advanced colorectal carcinoma. Haematological toxicity was manageable, with a short nadir for white blood cells and platelets. The response rate was 33%, with a prevalence in peritoneal lesions compared to liver or lung metastases. Extra-haematological toxicity appeared in 16% of cases: a case of veno-occlusive disease of the liver and two cases of lung impairment are discussed. Although the response rate obtained with the regimen was satisfactory, the more extensive use of high-dose chemotherapy followed by autologous bone marrow transplantation requires the identification of less toxic protocols.