The polymerization of diphenyldipropargylmethane was carried out with various transition- metal catalysts. It was found that the MoC15- and WCl6-based catalyst systems are very effective for the cyclopolymerization. The characterization of poly(diphenyldipropargylmethane) was carried out by IR,1H NMR,13C NMR, Raman, and UV-visible spectroscopies. The resulting polymer has a conjugated polyene backbone containing a six-membered cyclic structure. Poly(diphenyldipropargylmethane) was a dark violet solid of high molecular weight [Mn = (1-8) × 104], soluble in aromatic hydrocarbons, some ethers, and some ketones. The resulting polymer possesses excellent thermal and oxidative stability in air. In morphology studies of poly (diphenyldipropargylmethane), the fibrillar structure with a 200-300-Å-diameter range was observed by scanning electron microscopy. The electrical conductivity and the magnetic properties of the resulting polymer upon doping were changed and these changes were studied by morphology, IR, UV- visible, and ESR spectra. © 1990, American Chemical Society. All rights reserved.