A new quaternary alkaloid, pachygonine, and two known alkaloids, magnoflorine (1a) and O,O'-dimethylmagnoflorine (1b), were isolated from the roots of Pachygone ovaata Miers (Menispermaceae). The structure of pachygonine was established as 2a on the basis of spectroscopic evidence and its conversion to cocculidine methoiodide (2c).