Six new C-19-diterpenoid alkaloids, circinatines A-F (1-6), along with eight known compounds, were isolated from the roots of Aconitum hemsleyanum var. circinatum. Their structures were elucidated by extensive spectroscopic methods including NMR, IR, HR-ESI-MS and X-ray experiments. All compounds were evaluated for their cytotoxic activity against MCF-7, A549, HCT-116 and 786-0 human cancer cell lines.