The paper reports on novel gas sensing devices based on III-nitride materials. Both platinum GaN Schottky diodes as well as high-electron-mobility transistors formed from GaN/AlGaN heterostructures with catalytically active platinum gates were investigated. The performance of these devices towards a number of relevant exhaust gas components (H 2 , HC, CO, NO) was tested. The test gas concentrations as well as the composition of background gases were chosen to simulate exhaust gas emissions from lean-burn engines. We found that GaN-based devices with platinum electrodes are mainly sensitive to hydrogen and unsaturated hydrocarbons with a sizeable cross-sensitivity to CO. Furthermore a strikingly dissimilar gas sensing behavior has been observed with respect to saturated hydrocarbons on the one hand and to hydrogen and unsaturated hydrocarbons on the other hand.