Changes in arterial blood pressure and in thermographic values were evaluated in two groups of 15 hypertensive patients, each of which was treated, on a random basis, with a combination of atenolol plus chlorthalidone or a combination of labetalol plus chlorthalidone. Both combinations produced a statistically significant reduction in blood pressure values (p less than 0.01) with no changes in heart rate. Telethermographic investigations revealed the presence of hypothermia of the hands before treatment in all the hypertensive patients examined, but not in the control group (10 normal subjects with no vascular and/or hyperthermic disease). After one month of treatment, no changes in peripheral vascularization were observed in the group treated with atenolol plus chlorthalidone, except for 4 cases showing mild improvement, probably due to a reduction in peripheral resistance as a result of the treatment and to a consequent increase in blood flow in the area investigated. In the group treated with labetalol plus chlorthalidone, on the other hand, a substantial recovery of vascular flow was observed in 12 patients as a result of the treatment, while the remaining 3 patients showed a fair degree of improvement (2 degrees C). Both preparations lent themselves to simplified administration regimens with good patient compliance and no adverse reactions.