In another communication1 our associates and we have reported certain quantitative changes in the electroencephalogram following metrazol shock therapy. The subjects of that study were all patients with depressions. The significant changes in the electroencephalogram were found to be in the lower frequencies, those below 6 per second, these slow waves becoming more prominent after shock. No significant changes in alpha activity were noted, although in individual cases there were pronounced shifts upward and downward in the per cent time alpha. The present report is concerned with a similar study of the electroencephalographic changes following insulin shock treatment of patients with schizophrenia. METHOD Ten patients with schizophrenia, selected for treatment with insulin shock therapy, were utilized in this study. Nine of these patients received a similar course of thirty comaproducing treatments. Cortical potentials were recorded from the left occipital, the left motor and the left frontal area by means