A review of the available evidence shows clearly the rarity with which diabetics understand and follow their diet prescriptions. The reasons for these shortcomings and their persistence are many and complex. They include the tendency of physicians to underestimate the formidability of developing, implementing, and adjusting a diet prescription that is both acceptable and effective over a long period of time. Another problem is the limited conceptual and technical knowledge of most physicians concerning dietary principles, strategies, and tactics as they apply to the various types of diabetes. Recent research confirms the important potentials of diet regulation in mitigating diabetes and its complications. But apparently much of our effort in diet counseling is ineffective and wasteful. It seems desirable, therefore, to review in some detail the reasons for this failure and then to use candid appraisals for developing more effective approaches in the diet therapy of diabetes.