LaGaO3 (LSGM) based solid electrolyte coupled with suitable electrodes was demonstrated to be a highly sensitive hydrocarbon (C 3H6) sensor in the temperature range of 523-673 K. Sensors were studied in the amperotnetric mode. Keeping Pt as the active electrode, the various inactive electrode materials were studied. It was seen that La 0.5Sr0.5CoO3 (LSC 55) gave the best sensitivity among the studied LaCoO3 catalysts. Furthermore, it was found that the performance of the sensor with La0.5Sr0.5MnO 3 (LSM 55) showed the highest sensitivity (≈600 μ,A/decade at 623 K) among all the investigated perovskite oxides for an inactive electrode. The sensitivity of all the sensors was fast, reversible, and the current linearly increased with increasing C3H6 concentration. Over a broad range of oxygen concentration, the C3H6 sensitivity was found unaltered. The thickness of the LaGaO3 electrolyte played an important role for increasing the sensitivity. The measured value of the open circuit potential in the potentiometric mode was very small; but it confirmed the development of mixed potential between the two electrodes which palyed the key role for changing current in the present amperometric sensor. © 2004 The Electrochemical Society. All rights reserved.