A temporary strict blood glucose control was achieved by means of intravenous insulin infusion in 37 non insulin-dependent diabetic patients with secondary drug failure to reinduce the efficacy of oral hypoglycemic agents. This procedure was successful in 18 patients (48.6%) resulting in better glycemic response to oral hypoglycemic agents. Results remained identical 6 and 12 months later. This improvement does not seem related to an increase in insulin secretion as urinary C-peptide and basal and glucagon-stimulated plasma C-peptide were identical before and after insulin infusion. We suggest that a decrease in insulin resistance, not tested in this study, may explain the beneficial effect or normoglycemia in our patients.