An attempt is made to account for athetoid movements through consideration of the effects which inapproprioception (faulty proprioceptive feedback) might have on the physiological control system involved in coordination of voluntary motor outflow. The application of control systems theory to this problem is discussed in terms of pointing out central nervous system structures and functions which might correspond to the blocks and interconnections in the diagram which systems engineers use to represent a position control system. Since the sensitivity of muscle receptors is under the control of centrifugal modulatory mechanisms, one likely kind of malfunction in a limb position control system might be derangement of stretch receptor sensitivity. Desensitized stretch receptors might be responsible for random, purposeless athetoid movements which could be reflecting inaccuracy of position determination. If faulty sensory input is at the root of athetoid movements, then treatment must center around improving the quality of sensory inflow from the limbs and stabilizing the rest of the body while each part is brought under control separately.