Development of MoO 3 as a novel material for gas sensing was addressed. Thin films were produced by reactive rf sputtering assisted by annealing. Doping with Ti was performed to enhance the conductance of the MoO 3 film. It came out that the layers were two orders of magnitude more conductive than undoped material. Good and reversible response to CO was achieved at 300 o C, which fell off at higher temperatures. An interesting feature of the films was a considerably fast response for both CO and NO 2 despite low operating temperature. Doped films were found to operate at best about 100 o C below than for pure MoO 3 layers.