1. Insulin coma therapy at the Pennsylvania Hospital produced an immediate improvement or remission in 67.7% of 780 patients treated between 1936 and 1951.2. At least 334 patients, or 63.3% of all patients who originally improved, had a relapse; 44% of all these relapses occurred within 30 days, and 78% within 1 year of treatment. A second insulin course brought about an improvement or remission in 52% of 122 patients who had relapsed.3. Factors associated with the most favorable prognosis include: age over 16, psychosis of less than 6 months' duration, with a clinical picture of paranoid, catatonic, or undifferentiated schizophrenia; and if during treatment the patient receives at least 30 to 60 coma hours and gains more than 30 pounds in weight.4. We conclude that insulin coma therapy is effective in restoring the schizophrenic patient to his prepsychotic adjustment. This restoration to health is not accompanied by a permanent correction of the factors that predispose the patient to regress to schizophrenia.