This work investigates the use of NiO/Fe2O3 as a room temperature (R-T) polymer thick film gas sensor. To find the optimum ratio of NiO to Fe2O3, three compositions were prepared using different molecular percentages (75/25, 50/50 and 25/75 M wt.%) and prepared as a thick film paste. These pastes were then screen-printed onto glass substrates with interdigitated silver (Ag) electrodes. The final composition of each film was determined using XRD analysis. The films were used to detect methanol, ethanol, propanol, toluene, acetone and tetrahydrofuran (THF) at RT. The response of each device was defined using the formula, (R-gas-R-air)/R-air) x 100, where R-air is the resistance of the film in air and R-gas is the resistance of the film after the exposure to gas vapours. For each composition tested, the highest responses where displayed for toluene and propanol. The sensitivity was determined as the first derivative of response. Their sensitivity to 8000 ppm of toluene was calculated to be 0.008%, 0.0058% and 0.0059% per ppm for compositions with 75/25, 50/50 and 25/75 M wt.% of NiO/Fe2O3, respectively. Their sensitivity to propanol was found to be 0.0030%, 0.0029% and 0.0027% per ppm for compositions in the same order as listed previously. The fastest response and recovery times of each device were found after the exposure to 4000 ppm of toluene and propanol at room temperature. Sensor fabricated using composition 75/25 M wt.% of NiO to Fe2O3 showed response/recovery times of 30/45 s for propanol and 40/48 s for toluene. (c) 2005 Elsevier B.V. All rights reserved.