Two new bisbenzylisoquinoline alkaloids, isopyruthaline and isopythalines, were isolated from roots and rhizomes of Isopyrum thalictroides. The known alkaloid fangchinoline was isolated for the first time from a plant of the family Ranunculaceae. All structures were elucidated by physical and spectral studies. Copyright (C) 1997 Published by Elsevier Science Ltd.