The poly(phenylenevinylene) skeleton was selected as a magnetic coupler of polyradicals, because of its developed π-conjugation, coplanarity, and solvent-solubility even after substitution on the phenylene ring. By synthesizing poly(1,4- or 1,2-phenylenevinylene)-2- or -4-substituted with a stable phenoxy or nitroxy radical, an intramolecular, through-bond and long-range, but strong, ferromagnetic exchange interaction was realized for the first time. The polyradicals were chemically stable and, even at their spin concentration ofca. 0.5, displayedSvalues of 2/2 ∼ 4/2.