Laboratory studies in patients with autosomal-dominant hypertension and brachydactyly showed increased sensitivity to sympathetic stimuli and severe abnormalities in baroreflex buffering. To further elucidate the mechanisms by which impaired baroreflex sensitivity could influence blood pressure (BP), we conducted autonomic testing under field conditions. We studied 17 hypertensive affected (13 to 48 years, BMI 22.7 ؎ 6.5 kg/m 2 , 160 ؎ 23/98 ؎ 15 mm Hg) and 12 normotensive non-affected (9 to 60 years, BMI 24.0 ؎ 4.7 kg/m 2 , 120 ؎ 16/70 ؎ 10 mm Hg) family members. Pulse intervals and finger BP were measured using the Portapres device. Valsalva ratio, the blood pressure overshoot during phase IV of the Valsalva manoeuver, the Ewing coefficient (RR30/15 ratio), and heart rate and BP variability were similar in affected and non-affected family members. Overall, baroreflex sensitivity calculated using the cross-