From April 1981 to December 1981, 34 consecutive patients with advanced gastrointestinal cancer were treated with chlorozotocin at the dosage of 40 mg/m2 daily for 5 consecutive days (30 mg/m2 in patients pretreated with chemotherapy) every 6 weeks. In the 30 patients evaluable for response, a 3.3% objective response rate was encountered. Toxicity was not significant and consisted mainly in reversible myelosuppression. Median survival was 3 months. At the dosage and schedule used, chlorozotocin does not seem to be an effective agent in the treatment of advanced gastrointestinal cancer.