Arrays of electronic sensors, capable of detecting and differentiating complex mixtures of volatile compounds, have been utilized to differentiate aromas of food and related materials. These sensor arrays have been dubbed "Electronic Noses" and have been commercially available in the USA for the past 4-5 years. Electronic nose technology is still in its development phase, both in respect to hardware and software development. The instruments contain an array of from one to 32 sensors, using a variety of different sensor technologies--from organic polymers to metal oxides to micro-balances. Electronic noses are being widely used by some companies as a quality control instrument. Strengths include high sensitivity and correlation to human sensory panels for many applications. Limitations to their full potential includes loss of sensitivity in the presence of water vapor or high concentrations of a single component like alcohol; sensor drift and the inability to provide absolute calibration: relatively short life of some sensors; necessity to do considerable method development work for each specific application; and lack of being able to obtain quantitative data for aroma differences. They do have a high sensitivity (ppt to ppm) and are often more sensitive than the human nose. There is some evidence that sensors differentiate aromas on the basis of relatively few compounds and in the future a relationship between specific chemicals and a single flavor attribute may be achievable. Also, the possibility exists to differentiate between "top" and "middle" notes of aroma.