This chapter reviews (1) the sensory attributes with which the book is concerned, for example, the appearance, odor, flavor, and feel of different products; and (2) the mechanisms that people use to perceive those attributes, for example, the visual, olfactory, gustatory, and tactile/kinesthetic senses and sometimes sound. This chapter is brief, not because it is less important, but because many other books cover in depth the psychological and physiological mechanisms of sensation and perception. The sensory professional is urged to study the references for this chapter (e.g., Amerine et al., 1965; ASTM, 1968; Civille and Lyon, 1996; Lawless and Heymann, 1998; and Stone and Sidel, 2004) and to build a good library of books and journals on sensory perception. Sensory testing is an interdisciplinary science comprised of information and methods adapted from psychology, physiology, statistics, linguistics, medicine, chemistry, physics, sociology, anthropology, and a host of other fields. Experimental designs need to be based on a thorough knowledge of the physical, chemical, and psychophysiological factors behind the attributes of interest. Results of sensory tests often have several possible explanations; therefore, when interpreting these results, it is important to consider new knowledge about the senses, the true nature of product attributes, probability and risk management, and consumer behavior.