The metathesis polymerization of an anthrylacetylene bearing an alkyl ester group, 9-(10-hexoxycarbonyl)anthrylacetylene (1), was conducted with various transition-metal catalysts. A completely soluble black polymer was obtained from 1 in a good yield when W-based catalysts were employed. The polymerization at a high monomer concentration (1 M) and a high temperature (80 degreesC) led to the formation of poly(1) with a weight-average molecular weight of 297 x 10(3) in an 80% yield. The use of cocatalysts unexpectedly decreased both the yield and molecular weight of poly(1). Rh-catalyzed and Mo-catalyzed polymerizations, however, resulted in poor yields of the polymer. The ultraviolet-visible spectrum of poly(1) showed a significantly redshifted absorption (lambda (max) = 571) with a cutoff art 780 nm, which verified the very high order of conjugation of the main chain. Poly(1) exhibited the largest third-order nonlinear optical susceptibility [chi ((3)) (-omega; omega, 0, 0) := -1.9 X 10(-10) esu] among the polymers from the monosubstituted polyacetylenes synthesized so far. The electrical conductivity of poly(1) in an I-2-doped state was 8.77 x 10(-4) at 293 K.