Two new alkaloids, Septonine (C(35)H(44)N(2)O(9)) and Septontrionine (C(25)H(39)NO(6)) were isolated from the roots of Aconitum septentrionale K. According to the (1)H and (13)C NMR, IR, and mass spectra, Septonin and Septontrionin were assigned the structures of 20-ethyl-7-hydroxy-1 alpha, 14 alpha, 16 beta-trimethoxy-6-oxo-17(7 -> 8)abeoaconitan-4-ylmethyl 2-(2,5-dioxopyrrolidin-1-yl)benzoate and 20-ethyl-7-hydroxy-1 alpha, 14 alpha, 16 beta-trimethoxy-4-methoxymethyl- 17(7 -> 8)abeoaconitan-6-one, respectively.