Two new norditerpenoid alkaloids, leucostines A (1) and B (2), and a new diterpenoid alkaloid, 11-acetyllepenine (6), have been isolated from the root of Aconitum leucostomum. Their structures were elucidated on the basis of spectral data and chemical evidence. Four known alkaloids, delsoline (3), delcosine (4), lepenine (7), and songorine (8), were also isolated and identified from this plant for the first time.