Hinokiflavone (1) was isolated as the cytotoxic principle from the drupes of Rhus succedanea L. A comparison of the cytotoxicity of 1 and other related biflavonoids, including amentoflavone (2), robustaflavone (3), agathisflavone (4), rhusflavone (5), rhusflavanone (6) and its hexaacetate (7),