A series of novel 5,7-diamino-3-phenyl-2-benzylamino, 2-phenoxy, and 2-thiophenyl substituted quinoxalines has been designed, synthesized and evaluated for their in vitro antitumor activity towards cell lines of nine different types of human cancers. Some of these compounds exhibited inhibitory effects on the growth of a wide range of cancer cell lines generally at 10(-6) M, in some cases at 10(-7) M and 10(-8) M concentrations. Within this series the benzylamino quinoxaline derivatives 1b-7b were the most active, whereas compound 2c showed the highest MG_MD value (-5.66).