In the rat's olfactory bulb, the mitral cell multiunit activity in response to food odour changes with the internal states of food deprivation or satiety. It is demonstrated that stomach distension should be one of the factors acting on the centrifugal control of the olfactory input. An inflatable balloon was chronically inserted into the stomach of male rats trained to eat a single daily meal. The mitral cell responses to the usual food odour and to the control odour of isoamyl acetate were recorded in unanaesthetized fasted animals for 3 successive states of the stomach: empty, then inflated by introducing water into the balloon, and empty again. Stomach inflation produced a rapid, long lasting and significant decrease of the bulb responsiveness to food odour without changing the responsiveness to control odour. Stomach distension thus simulates the previously noticed effects of satiety on the selective modulation of the olfactory input.