The control of salicylate therapy by frequent estimation of the blood level requires a simple method suitable for use in a routine clinical laboratory. The method of Brodie. Udenfriend, and Coburn (1944) is generally accepted on account of its accuracy but is somewhat too laborious for a large number of estimations. A number of other methods are known but none has found general acceptance. Some of these were given preliminary trials in the summer of 1948. They were the methods of Camponovo (1945Camponovo ( , 1946, Barker (1936), Volterra and Jacobs (1947), Weichselbaum and Shapiro (1945), Coburn (1943), Mallick and Rehmann (1945), and Velez-Orozco and Guerra (1946). Camponovo's (1945Camponovo's ( , 1946