A new stereoisomer (I) of (—)-sophocarpine (II) was isolated from epigeal part of Sophora flavescens. The relative configuration and stereochemistry were determined by X-ray diffraction studies with monohydrate of free base. The absolute configuration was elucidated by chemical interrelation of I with (+)-matrine (III) and (+)-allomatrine (IV) of known absolute configuration. © 1978, The Pharmaceutical Society of Japan. All rights reserved.