ABSTRACT Hydrogen gas sensors based on semiconducting tungsten trioxide (WO3) were produced using a commercially attractive thick-film screen printing process. WO3 powders were doped with 1 mole % Pt or Pd and attrition-milled to produce precursor powders for sensor fabrication. The sensors were fired in air using various temperature/time profiles. SEM and XRD techniques were used to investigate the phase composition and microstructural properties. The influence of processing conditions, additives, sensor operating temperature and partial pressure of H2 gas on the response characteristics of the sensors was investigated. Sensors were also produced from un-doped material and tested under identical conditions to establish the baseline data. The data indicates that high-sensitivity H2 gas sensors can be produced through the manipulation of powder composition and processing conditions. The response characteristics of WO3- based sensors were found to be significantly influenced by the sensor operating temperature, the type of dopant used as well as the H2 gas concentration.