The importance of sensory factors (both the sensory properties of foods and sensory abilities of consumers) in food selection is widely accepted. Less recognized and understood are the effects of sensory stimulation on physiologic processes. Mere exposure to the sight, smell, taste, and textural attributes of foods elicits myriad digestive, endocrinologic, thermogenic, cardiovascular, and renal responses. The responses are rapid (generally occurring within minutes of sensory stimulation), small (relative to the magnitude achieved when food is actually being metabolized), and transient (returning to near-baseline levels within minutes). Nevertheless, they have been hypothesized to prime the body to better absorb and use ingested nutrients. They are termed preabsorptive or cephalic phase responses. This review summarizes current knowledge of stimuli that trigger cephalic phase responses and selected response features (eg, magnitude and type of enzymes or hormones released). Mechanisms by which cephalic phase responses may influence nutrient absorption and use are proposed. Current knowledge of the behavioral and physiologic importance of cephalic phase responses is limited, thereby hampering development of dietary recommendations for preventive or therapeutic interventions. Further study of several identified promising areas of application and other easily proposed situations may provide a basis for expanded medical nutrition therapy. J Am Diet Assoc. 1997; 97:406–410,413.