Salivary flow rates and electrolyte concentrations in patients surgically treated for primary aldosteronism were measured both pre- and postoperatively. In five patients dramatic increases in sodium-potassium ratios and rates of flow occurred in parotid, submaxillary, and whole saliva soon after the removal of an aldosteroneproducing tumor. In two others, who were not cured of their aldosteronism by surgery, there was no change in the salivary electrolyte pattern postoperatively. Measurement of the concentrations of sodium and potassium in saliva may be used not only as a diagnostic aid but as an early index of prognosis and recovery in this disease.