Two new dimethylpyrano-isoflavones, named erymildbraedin A (4) and B (5), were isolated from the stem bark of the Cameroonian medicinal plant Erythrina mildbraedii, along with four known ones, the linear congeners, scandenone (1), erysenegalinsein M (2), 5,4'-dihydroxy-2'-methoxy-8-(3,3-dimethylallyl)-2'',2''-dimethylpyrano[5,6:6,7]isoflavone (3), and the angular isoflavone eryvarin B (6), and two other compounds, fraxidin and scoparone. Their structures were elucidated by the usual spectroscopic methods and isoflavone effects on the growth of human breast, prostate, and endometrial adenocarcinoma cells were determined. Isoflavones 1, 3, and 6 strongly inhibited the growth of all three cell lines, supporting the notion that a non-oxidized isoprenyl group at C-8 is requisite for cytotoxic activity.