The first pi-conjugated poly(thioketene dimer) was synthesized via the homopolymerization of a silylthioketene dimer by a chemical oxidation-reduction process. The polymerization of trimethylsilylthiokenene dimer in the presence of FeCl3 (in CHCl3 at 70 degrees C for 24 h) gave the corresponding doped poly(thioketene dimer). After treatment of the doped polymer with an aqueous solution of ammonia, the neutral poly(thioketene dimer) was obtained with an incidental desilylation. The polymer obtained was soluble in DMF and DMSO. From gel permeation chromatographic analysis (DMF, polystyrene standards), the number-average molecular weight of the polymer was found to be 7460. The polymer showed low oxidation potentials derived from the thioketene dimer unit. An effective extension of the pi-conjugation was observed in the polymer.