The sense of smell and the olfactory system have been a subject of intrinsic interest for millenia. Inquiry into the structure and function of the olfactory system is based on a long tradition that dates back at least to the ancient Greeks. The mechanistic basis for the sensitivity and selectivity of this chemosensory detection system has always posed a challenge and remained largely a mystery. Recently, there has been a renaissance of interest in it and especially in the application of contemporary techniques of biochemistry and cellular and molecular biology. In this volume, current research utilizing these ap­ proaches is discussed in depth by a group of scientists who are among the current leaders in the applications of these techniques to the olfactory system. These authors address a wide range of questions that bear directly on the olfactory system but have broader biological implications as well. The various chapters have been grouped into five broad subject areas that emphasize diverse but related questions. "Transduction and Ligand-Receptor Interactions" considers the biochemical bases of stimulus access, interaction, transduction, elimination, and information processing.