Insulin sensitivity and insulin binding to monocytes were determined in seven normal subjects before and after one week's treatment with glibenclamide 2 mg three times daily. Glibenclamide administration produced a 60% increase in maximal specific insulin binding to monocytes. There was no effect on the blood glucose response to an intravenous bolus of insulin but fasting blood glucose was significantly elevated following glibenclamide treatment. Statistically significant changes in the fasting levels of plasma C-peptide and serum proinsulin were not detected.