To assess the short-term metabolic effects a long-acting non-sulphydryl ACE-inhibitor benazepril on glycaemic control in Type 2 diabetes mellitus and arterial hypertension, 10 hypertensive diabetic patients treated with glibenclamide were studied in a double-blind, crossover fashion over two 10-day periods in which either benazepril (10 mg/day) or placebo was given. At the end of the 10 day treatment, both blood pressure and plasma glucose concentrations were lower after benazepril versus placebo (benazepril, blood pressure: 143 +/- 11/83 +/- 5 mmHg, plasma glucose: 7.1 +/- 1.2 mmol/l; placebo: blood pressure: 157 +/- 10/99 +/- 2 mmHg, plasma glucose: 8.2 +/- 1 mmol/l, p < 0.05). In response to an oral glucose tolerance test combined with 1 mg intravenous glibenclamide, plasma glucose levels were lower after benazepril versus placebo (0-460 min: 8.4 +/- 0.8 versus 10.5 +/- 0.9 mmol/l, p < 0.05), whereas plasma insulin, C-peptide and glibenclamide concentrations were not different. It is concluded that a short-term administration of benazepril in Type 2 diabetes mellitus reduces blood pressure and improves blood glucose control, most likely by decreasing insulin resistance.