Circulatory autregulation is the phenomenon whereby an isolated organ can maintain a constant or almost-constant blood flow rate over a range of perfusion pressures. A mathematical model is developed, based on work reported in the physiological literature, and tuned to show that autoregulation can be accomplished by pressure-induced oscillations in arteriolar radius. Various features known lo be exhibited by skeletal muscle and by stretch receptors are incorporated in the model of smooth muscle surrounding the arterioles.