Bi2Sr2-x La (x) Co2O9 (x = 0, 0.02, 0.04, and 0.08) polycrystalline-layered misfit oxides have been prepared by solid-state reactions. Electrical property measurements indicated that all the samples are p-type semiconductors. The electrical conductivity decreased and the Seebeck coefficient increased with increasing temperature. The thermal conductivities were very low, only 0.6-0.7 W m(-1) K-1 at room temperature. La doping was effective in increasing the Seebeck coefficient, reducing the thermal conductivity, and hence improving the thermoelectric performance. A highest dimensionless figure of merit ZT of 0.147 was obtained for Bi2Sr1.96La0.04Co2O9 sample at 737 K, about two times higher than that of the sample without La doping.