The dynamic viscoelasticity of fractionated poly(3-hexylthiophene)titanium carbide (P3HT/TiC) composites was examined with regard to their electrical characteristics. The elastic modulus (E') at 0degreesC [i.e., near the glass-transition temperature (T-g) of P3HT] increased with increasing TiC content of the composite. In particular, composites whose TiC content exceeded the threshold concentration showed a high E'. This was caused by the high E' of TiC and the strong interaction between TiC and P3HT. When the sample was heated above the T-g, E' decreased rapidly and an increase in the loss tangent appeared near the Tg of P3HT. Mechanical loss was caused by friction between TiC and P3HT. The change in mechanical characteristics affected the electrical conductivity. When the TiC content of the composite approximated to the threshold concentration, a significant change in mechanical characteristics took place, so that a large positive temperature coefficient (PTC) effect was observed near the T-g. To explain the PTC phenomenon, we propose a model of conductive pathway for P3HT/TiC.