The motor defects of cerebral palsy, and the mental retardation that so commonly accompanies it, are chiefly clue to destruction of cerebral neurons. Such disorder is not as clearly indicated in the electroencephalogram as nondestructive, nonlethal, irritative injuries. Certain nonparoxysmal forms of electroencephalographic abnormality, for example, focal slowing, asymmetry, and altered sleep patterns, correlate fairly well with the structural damage and with the specific motor defects of cerebral palsy. The electroencephalogram is a sensitive indicator of less than lethal injury in damaged but surviving neurons, whose function is not abolished but is unstabilized. Such disorder commonly manifests itself in epileptic seizures. Although cerebral dysrhythmia and epilepsy are not the main problems in cerebral palsy, they should not be overlooked. They are related to the motor and intellectual manifestations and they are part of the total problem. Electroencephalography adds another dimension to our view of cerebral palsy. In combination with other parameters of evaluation is useful for diagnosis and prognosis and as a guide to treatment.