In 19251 there was reported a series of results obtained when the blood of patients with various forms of kidney lesions was tested for the diazo-color reaction by Hewitt's modification2 of Andrewes' original technic.3 The clinical value of this test was confirmed. Twenty cases in all were observed. It was then found that the reaction was obtained only in cases of severe kidney lesions. In all of the cases in which positive reactions were obtained, the values for blood urea nitrogen were high, ranging between 90 and 210 mg. per hundred cubic centimeters. The creatinine content of the blood specimens was also high. The reaction was not always associated with fatal termination. A patient who had severe nephritis during the course of pregnancy recovered. Nor was there perfect correlation between the degree of retention of urea and the reaction. This was shown in a case of bilateral renal tuberculosis with