The association of an abnormal electroencephalogram with obsessive-compulsive states has been investigated by Pacellaet al.(1944), who found in these states a higher incidence of “convulsive-type” patterns, consisting of occasional or frequent runs of serial 2–4 c/s potentials of high amplitude than in a random control group. In most of the cases this type of activity was only noted after a period of hyperventilation not exceeding two minutes.