The controversy over whether strict blood glucose control prevents or attenuates the complications of diabetes is still unresolved, but the available data support the value of good blood glucose control. The resolution of the controversy is not feasible at present because of the complexity and financial cost of a definitive prospective study and because we may not presently possess pharmacological agents which can accomplish the goal of long term strict control of the blood glucose. Finally, whereas we regard retinopathy, nephropathy and neuropathy as valid pathological endpoints, we are not secure in assuming that blood glucose represents the critical measurement for longitudinal assessment of metabolic control. Studies evaluating control based on blood and urine glucose assessments are complicated by the failure of the data to reflect changes in minute to minute regulation. Thus, the relative insensitivity of some of these parameters of control could account for failures to demonstrate a correlation between adequacy of therapy and diabetic complications.