The flowers of Catharanthus roseus (L.) G. Don enjoy the reputation in the folklore of possessing hypoglycemic properties and are, therefore, administered to diabetic patients. While a large amount of work has been carried out on the alkaloidal contents of the leaves of C. roseus (1-6), little work has been done on the flowers of this plant. We report here the isolation of ten alkaloids from its flowers: vinblastine, coronaridine, 11-methoxytabersonine, tetrahydroalstonine, ajmalicine, catharanthine, mitraphylline, vindorosine, vindoline, and a new alkaloid that appears to be isomeric to vincristine. © 1984, American Chemical Society. All rights reserved.