The work function principle of gas sensing is dedicated for room or slightly elevated temperatures of operation as signal contributions from both physisorption and chemisorption will be detectable. Prerequisite are FET transistors either with permeable gates made of palladium or polymers or with a suspended gate whose air gap permits the access of gases to the inner surfaces of the gate capacitance. The later design allows to incorporate almost all groups of sensitive materials, if a hybrid construction is used. The available models for metal oxide and electrochemical sensors can be adopted for comprehension of this surface potential method and for an estimative overview for the development of new sensors. The presented results show the vast capability of the work function principle leading to micro gas sensors with low power consumption suitable for low cost applications. Nevertheless, the general requirements for well operating gas sensors - high selectivity, high sensitivity, high stability and high S/N ratio - can be satisfied. (C) 2001 Elsevier Science B.V. All rights reserved.