The low temperature thermoelectric properties of TiSe2, co-doped with Cu and S, are reported. Partial S substitution for Se changes the magnitude of the indirect bandgap, while the Cu-doping independently controls the n-type carrier concentration. The Seebeck coefficients are negative, in the range of -50 to -200 mu V K-1, and the resistivities are 0.1-10 m Omega cm. The thermal conductivity for the sample with the largest thermoelectric power factor was found to be relatively low, 3-4 W m(-1) K-1, and decreases with decreasing temperature. The thermoelectric efficiencies for the best materials found in this system, typified by Cu0.02TiSe1.7S0.3, were largest at 0.07 at 300 K and decreased to 0.01 at 75 K. (C) 2008 Elsevier Ltd. All rights reserved.