The structure was elucidated of a polar, glycosidic alkaloid, cycloposine, from Veratrum californicum, known to produce fetal cyclopia and related central nervous system malformations in sheep. Data from I.R., N.M.R., mass spectrometry and other means identified the structure as 3-glucosylcyclopamine. Thus, it is the glycoside of another teratogenic alkaloid, cyclopamine (11-deoxojervine) and hence 3-glucosyl-11-deoxojervine. © 1969.