Effects of bisoprolol and atenolol on glucose metabolism in hypertensive patients NIDDM. The aim of the study was to compare the antihypertensive efficacy and the effects on glucose metabolism of a new beta 1-selective beta-blocker with high beta 1 selectivity, bisoprolol and atenolol in 12 hypertensive patients (WHO classes I e II) suffering from untreated not insulin-dependent diabetes mellitus (NIDDM). According to a cross-over design after a placebo run-in period of 4 weeks, the patients were randomly allocated to receive bisoprolol 10 mg o.d. or atenolol 100 mg o.d. for 4 weeks, with a four-week wash-out period between the two active treatments. In basal condition and after each therapy an intravenous glucose tolerance test (i.v. GTT, 20 g) was performed, with evaluation of serum glucose and insulin at 0, 15, 30, 60, 90, 120 minutes and glycosuria during the test. At the same time blood pressure, heart rate (supine, upright), ECG, laboratory tests were assessed and subjective tolerability was evaluated. The glucose and insulin responses to the i.v. GTT did not significantly change to basal condition. Similarly glycosuria did not show significative increment during the test with both beta-blocking therapies. Blood pressure and heart rate values were significantly reduced (p less than 0.001) after bisoprolol and atenolol treatment. During the study no side effects were reported and laboratory tests and ECG remained substantially unchanged. These data confirm the antihypertensive efficacy of bisoprolol and atenolol and demonstrate the absence of important effects of these drugs on glucose metabolism in hypertensive patients with NIDDM.