Although many of the reports of determinations indicate that cholesterol is increased in pregnancy, there is still lack of agreement as to the time when the increase begins, the amount and the cause of the gain. Greater importance is being ascribed to cholesterol, as shown by the constantly increasing number of papers on this subject in the literature. It is not known just what part it plays in the permeability of membranes, edema, nephritis, nephroses, pregnancy, resistance to infection, epilepsy, etc., but sufficient data have been accumulated to indicate that a marked change in cholesterol is intimately associated with these conditions, which undoubtedly are either the cause or the result of the change. Cholesterol is found in both the erythrocytes and the plasma, occurring as the free alcohol and also as the ester of the fatty acids. In addition, certain other combinations or adsorption products of cholesterol and serum protein