Patients with Type I, i.e., insulin-deficient diabetes, Type II or non-insulin-deficient diabetes, and impaired glucose tolerance or so-called chemical diabetes are variably predisposed to develop macroangiopathy, i.e., atherosclerosis, microangiopathy or basement membrane thickening, and neuropathy. Once these morphologic changes appear, they in all probability will remain irreversible even when precise regulation is attained. Hence prevention is the only realistic goal.