A breath analyzer for alcohol will be designed for clinical use based on two new developments in electrochemical technology. (1) A new sensor that is not sensitive to carbon monoxide (on the breath of smokers). (2) A coulometric measurement technique, developed for CO measurement, that gives rapid answers and is insensitive to temperature and sensor aging. We will design, build, and test three prototype analyzers in Phase I. In Phase II, the prototypes will be tested in clinical environments and the prototypes will be redesigned based on user feedback.