This review presents the recent developments in electronic noses (E-noses). E-noses based on metal oxide semiconductors, conducting polymers, quartz crystal microbalance and electrochemical methods have been examined with regard to several aspects, from the basic principles to the application of new products, as olfactometry sensors. E-noses consist of an array of chemical sensors, and are currently employed in the analysis of odorous compounds as well as for common gas detection. Various data analyses have been employed to establish patterns of recognition and classification techniques. Future trends and areas of application for e-noses have also been introduced and are summarized within the text.