Eleven alkaloids have been isolated from the roots of Thalictrum simplex L. Thalicmine, thalicminine, β-allocryptopine, and magnoflorine have been found in this species for the first time. Thalicmidine and thalictrisine are new alkaloids. The main alkaloids of this species of plant are hernandezine in the tertiary fraction and magnoflorine in the quaternary fraction. © 1973 Consultants Bureau.