Cirrhotic patients have disturbed systemic hemodynamics with reduced arterial blood pressure, but this has not been investigated during daily activity and sleep. Systolic (SBP), diastolic (DBP), and mean arterial blood pressure (MAP), and heart rate (HR) were measured by an automatic ambulant device for monitoring blood pressure in 35 patients with cirrhosis and 35 healthy matched controls. During the daytime, SBP, DBP, and MAP were significantly lower in the patients than in the controls (median 118 vs. 127; 70 vs. 78; 86 vs. 94 mm Hg, P < .0001 to P < .05). The nghttime blood pressures were almost similar in the two;@oups (108 vs. 110; 65 vs. 67; 78 vs. 82 mm Hg, NS). Conqkrsely, HR was significantly higher in the patients both&h the daytime (86 vs. 72/min, P < .0001) and at night (80 vs. 64/min, P < .0001). Consequently, the reduction in, blood pressure and HR from daytime to nighttime was significantly lower in the patients than in the controls (P < .0001 to P < .01). Multiple regression analysis showed HR, serum albumin, serum sodium, and clotting factors 2,7, and 10 as significant independent predictors of SBP in cirrhosis. In conclusion, cirrhotic patients have elevated HR, but surprisingly normal arterial blood pressure during the nighttime, and the circadian variation in blood pressure and HR is diminished, probably because of an almost unaltered cardiac output during the 24 hours. These results may reflect a major defect in the ability of optimal regulation of blood pressure in cirrhotic patients. (HEPATOLOGY 1995;2288-95.) Cirrhotic patients often present with a deranged systemic circulation.' An important feature in the circulatory changes seems to be a marked arteriolar vasodilatation in splanchnic and peripheral tissue^,^,^ leading to decreased systemic arterial blood pressure and vascular resistance, and increased heart rate (HR), cardiac output, and plasma volume.'-5 Previous studies have Abbreviations: HR, heart rate; SBP, systolic blood pressure; DBP, diastolic blood pressure; MAP, mean arterial blood pressure.