Nifedipine-induced hyperglycaemia in rats was counteracted by concurrent administration of metformin (500 mg/kg p.o). However, glibenclamide (5 mg/kg p.o.) did not change the hyperglycaemic effect of nifedipine. It is suggested that nifedipine-induced hyperglycaemia was not related to pancreatic effect and might be attributed to extra pancreatic mechanism by preventing the action of insulin in the tissues. Therefore, counteraction of nifedipine-induced hyperglycaemia by metformin, may play a role in diabetic patients treated with nifedipine.