Research into the characteristics of semiconducting metal-oxide films that are stable at high temperatures intensified with the aim of providing reproducible-and reliable gas detection in various ambients. First, there is a discussion of the specifics relating to these materials, for example, the effect of grain-boundary barriers on the sensing mechanism, :the influence of humidity, and the temperature dependence of the sensing mechanism. Then, the technology for the preparation of the gas sensors will be described. Examples that have already been implemented like lambda. detection, oxygen and NOx measurements in exhaust gases, detection of explosive and toxic gases in air, as well as hydrogen leakage detection are discussed.