Pt-doped mesoporous indium oxide (In2O3) has been successfully obtained by a simple and effective in situ nanocasting method. The resultant samples were characterized by XRD, FE-SEM, TEM, N-2 physisorption, XPS and EDX. The gas sensing properties for hydrogen sulfide (H2S) of the Pt-doped mesoporous In2O3 specimens were also examined. The results exhibit those In2O3 specimens possess much higher response to H2S even at low concentration of 2 ppm and a lower optimum working temperature of 150 degrees C. A possible mechanism was also provided to explain the improvement of the sensing properties. (C) 2010 Elsevier B.V. All rights reserved.