A phase-II study of vindesine was carried out in 23 patients with histologically proven advanced breast carcinoma. Toxicity was assessed in a further 24 patients with several different tumour tupes. Treatment was given in a starting dose of 3 mg/m2 weekly by IV bolus, increasing by 1 mg weekly as toxicity allowed. The response rate in 21 evaluable patients with breast carcinoma was 29%. In 47 patients evaluable for toxicity, leukopaenia occurred in 45% and was doserelated; thrombocytopaenia was rare (4%); neurotoxicity occurred in 40%; constipation in 17%, alopoecia in 46% and an influenza-like syndrome in 21%. It was concluded that vindesine was a clinically active agent in breast carcinoma, with a spectrum of toxicity lying between those of vincristine and vinblastine.