A new C20-diterpenoid alkaloid, yesodine (1̃), a new C19-diterpenoid alkaloid, yesoensine (2̃), and two known alkaloids, macrocentridine (3̃) and subcusine (4̃), were isolated from Aconitum yesoense var. macroyesoense (Nakai) Tamura. Structures of those new alkaloids were determined on the basis of their spectra and chemical correlation with known alkaloids. © 1990.