Disturbances of electrolytes in renal insufficiency have been recognized for many years, and in recent years emphasis has been laid on disturbances in the concentration of potassium in the serum and the effect of these changes on the electrocardiogram. Flaccid paralyses have been reported to be associated with both low1and high2concentrations of serum potassium. Instances of flaccid paralysis with increased concentrations of serum potassium as described by Finch and co-workers2were not observed by Keith and Burchell3in their experience with renal insufficiency, although special efforts were made to find them. The case herein reported illustrates the occurrence of flaccid paralysis in renal insufficiency with hyperkaliemia and demonstrates the use of the electrocardiogram in the immediate differentiation from hypokaliemia. REPORT OF A CASE A 49 year old housewife was admitted to a Rochester hospital on June 13, 1950, with a chief complaint of weakness