The objective of this study was to determine the cytotoxicity, antiproliferative activity, and apoptosis induction activity of two modified glycosides - digoxin and proscillaridin A - conjugated to a generation 3 polyamidoamine dendrimer (G3 PAMAM-NH(2)) in human breast cancer cells. The results suggest that conjugation with the G3 PAMAM-NH(2) dendrimer enhances the cytotoxicity of modified digoxin and proscillaridin Aboth in MCF-7 and in MDA-MB-231 breast cancer cells. Additionally, the conjugate-induced apoptosis was significantly greater than apoptosis evoked by free modified digoxin and proscillaridin A.