In cases of typical Addison's disease the diagnosis is usually not difficult, but periodically cases are encountered in which the clinician desires all possible help in establishing or excluding this possibility. To this end a laboratory procedure was proposed in 1938 by Cutler, Power and Wilder.1They showed that when patients who had Addison's disease were placed on a specified diet and intake of fluids they excreted consistently higher concentrations of sodium and chloride in the urine than did patients following the same regimen who did not have Addison's disease. These authors stated: "The... procedure suggested requires fewer days for completion, subjects the patient to less risk of collapse, and in most cases is quite as informative as the six day period of restricted intake of salt heretofore resorted to for diagnostic purposes." The present paper deals with the results obtained in the application of this procedure during the