The increase of inorganic sulphates in the serum in cases of renal insufficiency with azotemia has been demonstrated by Denis,1Loeb and Benedict,2and Wakefield.3The investigations of Wakefield led us to believe that the accumulation of further data which might be correlated with other tests of renal function would be of practical value. Wakefield and Power4developed a volumetric method5for the determination of serum sulphates which we believe to be dependable; the present research, therefore, has been carried out with the object of establishing the significance of inorganic sulphates in the serum in early renal insufficiency. Concentrations of inorganic sulphates in the serum could not be evaluated in clinical studies until the normal range was known. To establish the normal range, persons were observed whose medical history had been taken and whose general examination, including laboratory examination, had shown them to be normal.