1. A new alkaloid of composition C38H40O7N2 was isolated from the leaves and seeds of Thalictrum simplex L. 2. On the basis of a study of the products of reduction, oxidation, and cleavage with sodium in liquid ammonia thalcimine was assigned to the series of bimolecular bisbenzylisoquinoline ether bases. A structural formula is suggested for thalcimine. © 1966 Consultants Bureau.