Abstract: Cycleaneonine (Ⅰ), a new bisbenzylisoqainoline alkaloid, has been isolated from the roots of Cyclea racemosa Oliv. (Menispermaceae) growing wild in Siehuan Province. The structure of cycleaneonine was established as (Ⅰ) on the basis of spectral analysis (UV, IR, MS, ¹HNMR, ¹³CNMR) and physicochemical properties. It is a head-to-tail bisbenzylisoquinoline alkaloid possessing a substituted p-xylyl moiety, the first example having been found in the genus Cyclea.Cycleaneonine was found to show significant inhibitory activity against human carcinoma of the stomach cells carried in cell culture.