The error in a diabetic is essentially a carbohydrate intolerance, and correction of this defect should be aimed at in treatment.Dietetic treatment of diabetes is more readily studied in early cases or cases in the pre-diabetic state, before arterial degeneration and other catastrophes have become manifest. It is suggested that such a condition exists in obese subjects with a carbohydrate intolerance.A high protein diet based on a study of these cases is brought forward.This diet has been shown to operate favourably in diabetic states. Many cases of reasonable severity can be brought to develop a normal or nearly normal glucose tolerance curve and retain this state over a period of years. Cases in this state are better able to resist concomitant infections without deterioration of their tolerance than cases imperfectly balanced with insulin.The high protein diet can be used in cases of hyperpiesia in the absence of gross kidney damage. These cases show a steady and lasting drop in blood-pressure without the necessity of employing rest.The value of the pure fruit diet in increasing tolerance of certain diabetics to carbohydrate is demonstrated.The indiscriminate use of insulin in hyperglycaemic states is deprecated on the grounds that it is frequently unnecessary, and though it may balance it does not necessarily rectify the main deficiency of carbohydrate intolerance.By the use of this simple high protein diet, where no weighing, &c., is required, a large number of diabetics at present on insulin could be readily dealt with, a return to a normal or nearly normal glucose tolerance curve being obtained and maintained.