The authors conducted a clinical investigation in twenty-five patients affected with essential hypertension of mild or moderate grade associated with type II diabetes mellitus, the purpose being to assess the effect of 8 weeks of combined treatment with atenolol (100 mg) and chlorthalidone (25 mg) on arterial blood pressure, heart rate, and glycaemia. It is, indeed, generally known that both beta-blockade agents and diuretics can interfere with carbohydrate metabolism. The results indicate that 92% of the patients treated in this trial had significant reduction of systolic and diastolic blood pressure readings, in the absence of bradycardia or other adverse effects. Glycaemia values were lower at the end of treatment, probably as a result of better diet control during the trial, as suggested by the general tendency to body-weight reduction.