The isolation and structure elucidation of catharanthamine (3), a new bisindole alkaloid with antitumor activity from Catharanthus roseus, is described.Vincaleukoblastine (VLB) and leurocristine (VCR) are the most important bisindole alkaloids for the clinical management of many cancerous states (2, 3), yet there is still a pressing need for new, more active, and less toxic agents. It was with this aim in mind that we began to investigate a number of highly active alkaloid fractions of Catharanthus roseus (L.) G. Don (Apocynaceae) which did not contain any of the major antitumor alkaloids from this plant. A post-VCR alkaloid chromatographic fraction obtained through the courtesy of the Eli Lilly Co. (5) was subjected to pH gradient fractionation (6). Evaluation of the anticancer activity in vivo and in vitro indicated that activity was concentrated in the pH 5.0, pH 5.5 and pH 9.0 fractions (table 1). Extensive chromatographic separation has been made of these fractions (8) with concomitant bioassay. One of the biologically active alkaloids isolated during the course of this work, catharanthamine, is the subject of the present disclosure. This is the first bisindole alkaloid having oxygenation at C-17 of the velbanamine unit to be isolated and is, therefore, of considerable biogenetic interest.