The broad biological effects of isoquinolines prompted us to use them as chelating, nonleaving ligands in cis-platinum(II) antitumor complexes. The synthesis of several 1-(2-aminophenyl)isoquinoline derivatives with different levels of hydrogenation and varying substitution of the phenyl ring is reported. These compounds constitute a new class of ligands for the synthesis of oligocyclic platinum(II) complexes. In vitro cytotoxicity tests indicate that the most basic amine ligands afford the most effective complexes. Two of the new complexes were more potent against L1210 murine leukemia cells than the well-established antitumor compound cisplatinum.