Two new diterpenoid alkaloids, racemulosines A (1) and B (2), were isolated from the roots of Aconitum racemulosum FRANCH. The structures of the new alkaloids were elucidated by analysis of physical and spectroscopic data, and the structure of 1 was further confirmed by a single-crystal X-ray diffraction analysis. Furthermore, compound 1, at 2.25.10(-4) mol/l, showed moderate activity against platelet aggregation induced by PAF (platelet-activation factor).