In a double-blind crossover study, the influence of bisoprolol and placebo was tested in 20 noninsulin-dependent diabetics with concomitant essential hypertension. A 2-week washout placebo period was followed by two treatment periods of 2 weeks each with 10 mg bisoprolol or placebo. Compared with placebo, bisoprolol did not change blood glucose, haemoglobin A1 (HbA1), and glucosuria. No hypoglycaemia was observed. Serum cholesterol and triglyceride levels remained constant. Systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were significantly (p less than 0.01) reduced after 2 weeks of bisoprolol therapy, compared with placebo. It was concluded that bisoprolol, in a dose therapeutically effective in essential hypertension, has no influence on carbohydrate and lipid metabolism in noninsulin-dependent patients with diabetes mellitus; and 10 mg bisoprolol is effective for the normalisation of SBP and DBP in mildly hypertensive diabetics. Since bisoprolol was well tolerated in the dosage studied, it can be recommended for noninsulin-dependent diabetics with hypertension.