Two tracking experiments were carried out to investigate the motor control system in adults with cerebral palsy. The first experiment analysed the frequency response characteristics and the surface electromyogram from biceps brachii and triceps brachii, when the cerebral palsy subjects made isometric contractions during the pursuit tracking task with sine wave targets. Patterns of reciprocal innervation of the antagonists explained the frequency response characteristics of tracking behavior of the cerebral palsy subjects. The second experiment analysed perceived response velocity during the compensatory tracking task by means of magnitude estimation method. Fitting power function to the relation between the input frequency and the perceived response velocity, coefficients of determination for the cerebral palsy subjects were found to be lower than those for the normal subjects. It suggests that the cerebral palsy subjects can discriminate their response velocity less exactly than the normal subjects in manual tracking system.