Two new alkaloids, corydamine hydrochloride, C20H19O4N2Cl, mp 235—239° (decomp.) and N-formyl corydamine, C21H1804N2, mp 159.5—160.5°, were isolated from Corydalis incisa pers. (papaveraceae) and their structures were established to be II and IX, respectively, by spectroscopic analyses and their chemical conversion to coptisine iodide and anhydrodihydroprotopine-B. Corydamine hydrochloride and N-formyl corydamine are noted as the first naturally occurring alkaloids having the 3-phenyl isoquinoline skeleton. © 1973, The Pharmaceutical Society of Japan. All rights reserved.