Neurones in the lateral hypothalamic region are described which alter their firing rates when a monkey looks at food. The units responded when the monkey looked at different types of food, but not at non-food objects or simple visual stimuli. The units did not respond in relation to motor movements, intense arousal, nor when a salient aversive stimulus was shown, nor in relation to eye movements, and were thus shown to be different from units in the globus pallidus which did respond in some of these control tests. The neurones did not respond to olfactory stimuli and did not respond if the animal ate in the dark. Because of these findings it is suggested that the activity of these hypothalamic neurones is associated with the sight of food. It is of interest that these neurones which respond when food is shown to a hungry animal are found in a region thought to be involved in the control of feeding.