The alkaloid compositions of four species of plants of the genus Argemone (A. mexicana L., A. alba L., A. platyceras Link et Otto., and A. hybrida) collected in the flowering phase in the Tashkent Botanical Garden have been studied. They have yielded 16 alkaloids. Corydine and isocorydine have been detected in plants of this genus for the first time, and O-methyl-platycerine has been found in nature for the first time. © 1986 Plenum Publishing Corporation.