Sb0.2Bi1.8Te3 Thin Films were grown using the thermal evaporation technique on a (001) face of NaCl crystal as a substrate at room temperature. The optical absorption was measured in the wave number range 500 cm(-1) to 4000 cm(-1). From the optical absorption data the bandgap has been evaluated and studied as a function of the film thickness and deposition temperature. The data indicate absorption through direct interband transition with a bandgap around 0.21 eV. The detailed results are reported. (C) 2003 Kluwer Academic Publishers.