A novel electroconductive polypeptide gel based on a formation of a charge-transfer (CT) complex between poly(L-lysine) (PLL) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) was prepared. The PLL gel extensively swelled in dimethyl sulfoxide (DMSO) containing TCNQ and showed a dark green color to give PLL(+)TCNQ(-). Differential scanning calorimetric (DSC) measurement showed a significant depression of the melting temperature. The electrical conductivity of the PLL(+)TCNQ(-) gel below melting temperature of DMSO was nearly 3 orders of magnitude higher than the corresponding solution. These phenomena were explained in terms of the extensive association of DMSO molecules with the charged network through strong electrostatic interaction.