A redox-active alternating pi-conjugated copolymer of ferrocene with dithiafulvene was synthesized by cycloaddition polymerization of aldothioketene derived from 1,1'-bis(trimethylsilylethynyl)ferrocene (1). The obtained polymer (2) was soluble in common organic solvents such as THF, CH2Cl2, CHCl3, DMF, and DMSO. The structure of 2 was confirmed by IR, H-1 NMR, and C-13 NMR spectra compared with those of a,6-bis(ferrocenyl)-1,4-dithiafulvene as a model compound (3). The cyclic voltammogram of 3 showed three oxidation peaks, which were originated from the two ferrocene units and the dithiafulvene unit. The polymer 2 showed only single-broad oxidation peak at 0.58 V vs Ag/Ag+. This result was caused by an effective interaction between two different donors in 2. Compounds 2 and 3 did not undergo oxidative dimerization to form extended tetrathiafulvalene during cyclic voltammetry. The polymer 2 formed a soluble charge-transfer (CT) complex with TCNQ in DMSO. The ratio of the dithiafulvene unit in 2 to TCNQ in the complex was 1:1, confirmed by 1H NMR. The electrical conductivity of 2 was 3.6 x 10(-3) S/cm after I-2 doping.