A phase II study of vindesine was carried out in 33 patients with colorectal cancer and nine patients with esophageal cancer. With the exception of six previously untreated patients with esophageal cancer, all others were refractory to 5-FU-containing regimens, w,hich included vincristine in ten patients. The initial dose of vindesine was 4 mg/m2 administered intravenously over 30 min every 2 weeks. Tumor regression less than 50% was set patients (six colorectal and two esophageal) achieved minor responses. Prior treatment with vincristine did not seem to influence response to vindesine. In general, the treatment with vindesine was well tolerated. The hematologic toxicity was acceptable and manifested mainly as moderate and transient neutropenia. The major nonhematologic toxicity was peripheral neuropathy, which became limiting. It occurred in 33% of patients who received two or more courses of vindesine. Because of the apparent antitumor activity and dose-limiting neurotoxicity of vindesine in this sutdy, further investigations of this compound should be conducted in combination chemotherapy programs for patients with metastatic gastrointestinal cancers.