ZnO:Sb based screen printed thick-film H-2, CO and CH4 gas sensors were fabricated. Films were realized on an alumina substrate by mixing ZnO with lead borosilicate glass frits as a binder and Sb as a catalyst. It was observed that the ZnO:Sb based sensors were more sensitive to these gases than the pure ZnO sensors. The conductance of the sensor increased linearly with the square root of the gas concentration. The dependence of the sensitivity on the amount of the additive (Sb) is discussed. The sensors have a response time of 10 a. Material characterization was carried out by using bulk X-ray diffraction (XRD) and surface morphology by scanning electron microscopy (SEM).