A potentiometric type electrode based on an oxidation-reduction reaction has been developed for gas measurement by attaching a permeable membrane to a conventional composite electrode, and this electrode has been applied to the measurement of soup aroma. Using an ammonia gas electrode and a hydrogen sulfide gas electrode together with the oxidation-reduction gas electrode system, we have inspected the basic responses of such plural sensor systems with regard to the indicator components of an aroma derived from the process of cooking soup. These sensors showed characteristic responses for pyrazines, furans, sulfides, aldehydes and ketones that are important components in the aroma of soup. When applied to the measurement of aromas of consomme and chicken soups, the system was able to detect characteristic signals from individual sensors with regard to the different kinds of soups. The response of the oxidation-reduction sensor was larger than that of others regarding the diurnal quality change of soup. A deterioration of soup quality with the elapse of time was able to be identified by a method of principal component analysis using the signals of three sensors.