The structural elucidation of a variety of new isoquinoline-type alkaloids from Thalictrum fendleri has previously been reported, involving thalifendlerine (I), thalifendine (II), thalidastine (III), thaliporphine (IV), preocoteine (V), and thalidezine (VI). In addition, the presence of known alkaloids including berberine (VII), jatrorrhizine (VIII), glaucine (IX), magnoflorine (X), ocoteine (XI), hernandezine (XII), and thalicarpine (XIII) in T. fendleri was indicated. The purpose of the present paper is to describe the isolation procedure employed to obtain these 13 compounds. Additionally, the isolation of thaldimerine (XIV), a completely new dimeric aporphine-benzylisoquinoline alkaloid, is discussed, although lack of sufficient material has so far precluded its complete structural elucidation. A novel procedure for the separation of tertiary alkaloids is described, which consists of partition chromatography of the mixture of hydrochloride salts using a cellulose column in the methyl ethyl ketone-water system.