The objective of this study was to test the influence of bisoprolol and verapamil on left ventricular filling in hypertensive patients in a 6 month randomized, double-blind trial in 54 hypertensive patients not previously treated with beta-blockers or calcium inhibitors. After administration of placebo for 14 days, an M echocardiogram of the left ventricle was recorded to determine left ventricular mass. Blood flow was evaluated by pulsed Doppler sonography. After randomization into two groups, one group received 10 mg of bisoprolol and the other 240 mg of verapamil LP in a single dose in the morning. After 2 months’ treatment, the patients whose blood pressure was not well controlled were given a diuretic. Echo-Doppler was performed again by the same operator after 4-10 days on active treatment, after 6 months and after a subsequent 2 weeks of placebo for the patients treated with a single drug. The reduction in blood pressure was comparable in the two treated groups, but there was no significant decrease in left ventricular mass. Left ventricular filling was improved only in the patients receiving bisoprolol. The effect was observed immediately after the first administration and throughout the 6 months’ treatment period declining slowly during the placebo wash-out. This effect appeared to be independent of any alteration in heart rate and was thought to be a specific action of this drug.