Study on the phytochemistry of Aconitum hemsleyanium var. circinacum led to isolate two new C19-diterpenoid alkaloids, hemsleyanines A (6) and B (7) together with six known alkaloids, yunaconitine, talatisamine, hemsleyadine, hemsleyasine, hemsleyanidine and isohemsleyanidine. The structures of these alkaloids including new alkaloids hemsleynines A and B were established on the basis of spectral data (1H- and 13C- NMR, 2D NMR, HRMS) and X-Ray analysis. © 2005 Japan Institute of Heterocyclic Chemistry.