In order to determine the degree of metabolic control (HbA1c [normal less than 5.8%], mean blood glucose [MBG], glucosuria and lipids) and the prevalence of late diabetic complications in insulin-dependent diabetic patients treated by conventional insulin therapy both patients of a diabetes center (DC: n = 130; age 37.1 +/- 1.4 years) and a rural area (RA: n = 73; age 38.4 +/- 2.4 years) were examined within their local setting. Eighty such insulin-dependent diabetic patients were also taught a technique of near normal glycemic insulin substitution (NIS), which separates basal from prandial insulin replacement and instructs the patients to immediately correct self-controlled (3.8 +/- 0.1/day) aberrant blood glucose values. None of the groups on conventional insulin therapy was able to achieve satisfactory metabolic control or to avoid late diabetic complications, but rural patients were even worse off (BG 240 +/- 10 mg/dl; HbA1c 8.7 +/- 0.2% [normal: 3/73 = 4%]) than those of the DC (MBG 191 +/- 5 mg/dl; HbA1c 7.1 +/- 0.2% [normal: 27/130 = 21%]), while the prevalence of late diabetic complications was almost identical (RA/DC: neuropathy 22%/25%; retinopathy 41%/38%; macroangiopathy 15%/13%; but proteinuria 14%/5.4%). Metabolic control was improved by NIS with twice daily injections of basal (long acting) and separately of prandial (regular) insulin (total: 4.8 +/- 0.1 injections/day; MBG 130 +/- 2 mg/dl; HbA1c 5.8 +/- 0.1% [normal: 41/80 = 51%]. We conclude (1) that conventional insulin therapy just prevents metabolic catastrophe but in more than 79% of insulin-dependent diabetic patients lacks the ability to provide good metabolic control, while (2) NIS, a more physiological form of insulin therapy, improves this deplorable situation 5- to 12.4-fold.