Much of the potential of sensory information for understanding primate feeding has been ignored because the subject is usually approached from a nutritional perspective rather than a sensory one. However, nutrients are abstract constructs of modern science, so how can we expect primates to know what they are? To argue that a foraging primate is avoiding fiber or searching for a particular nutrient class such as protein, we have to establish a sensory link to these abstract food components. This review synthesizes widely scattered information on the sensory ecology of primates and asks how the senses might convey information on food location, abundance, and quality. Primates receive a barrage of sensory inputs, which help them make efficient feeding decisions about food distributed in time and space. We do not treat these senses in a traditional manner, but divide them into those that receive input from outside the animal (external senses) and from inside the digestive system (internal senses). We treat less completely some areas that have been reviewed in past issues of Evolutionary Anthropology, such as color vision, taste, and food physics.