D.C. Conductivity measurements on the thin films of a-Se78-x Te22Bix system (where x = 0, 0.5, 2 and 4) are reported in the temperature range 213-390 K and the density of states (DOS) near the Fermi level is calculated using dc conductivity data. It is found that the conduction in all the samples takes place in the tails of localized states. The conduction in the high temperature region 296-390 K is due to thermally assisted tunneling of electrons in the localized states at the conduction band edge. In the low temperature region 213-296 K conduction takes place through variable range hopping in the localized states near the Fermi level. (C) 2003 Kluwer Academic Publishers.