The plant Papaver macrostomum Boiss. et Huet was found to contain two new alkaloids which were named sevanine and macrostomine. Sevanine, obtained from the phenolic fraction (m.p. 218°), showed M+ at mass 309.0980 corresponding to C18H15NO4. Its UV spectrum was practically identical with that of papaverine, and PMR spectrum (CDCl3) indicated methoxyl, benzylic, methylenedioxy, and aromatic protons, leading to the structure 1-(3,4-methylenedioxybenzyl)-6,7-hydroxymethoxyisoquinoline (I). Chromatography on alumina of the nonquaternary fraction gave macrostomine (m.p. 107-110°, [α]D25 -51° ± 3°), with M+ 406.1892 corresponding to C24H28N2O4. Its UV spectrum was similar to that of sevanine, and PMR spectrum (C6D6) showed N-CH3, pyrrolidine moiety, methoxyl, methylenedioxy, benzylic, and aromatic protons, leading to structure II. The negative longest wavelength Cotton effect of macrostomine, similar to (S)-(-)-nicotine or (S)-(-)-brevicolllne, suggested its configuration may be S.