1. A study of the blood cholesterol in schizophrenia is presented.2. Many of the factors which might alter the blood cholesterol other than that induced by the mental disorder itself are investigated.3. There is a definite tendency to a lowered blood cholesterol in schizophrenia as a group.4. There are cases of schizophrenia in which the blood cholesterol is normal or increased, but the majority of cases show values below the lower limit of normal or in the lower limits of the normal range.