The immediate results of the use of protamine zinc insulin in diabetes have been frequently discussed. The effect of the prolonged use of protamine zinc insulin has not been so carefully considered. Ralli and her co-workers1gave a discouraging account of their experience with twenty patients at Bellevue Hospital. Graham2believes that protamine zinc insulin "will be the most popular method and will prove to be the best for the easy cases," though he cautions against premature enthusiasm until more experience has been obtained with it. McCullagh3found that sixty cases of diabetes responded exceedingly well to the prolonged use of protamine zinc insulin; Priscilla White4reported remarkable success in children: "95.0 per cent (574 patients) were known to be taking either protamine zinc insulin alone or in combination with regular insulin." Boyd and Jackson5obtained indifferent results in children, which they explained by the