In portal hypertensive patients and experimental models, hyperdynamic circulatory disturbances associated to a reduced peripheral resistance and an increased cardiac output appeared. The aim of this research is the study of the baroreflex system behavior partially portal vein ligated-portal hypertensive rats. Sham operated rats (S) (n = 7) and portal hypertensive rats (PH) (n = 9) were used. In anesthetized rats, catheters were introduced into a jugular vein for drug injection and into the ventral tail artery to record blood pressure and heart rate. When rats were conscious and moving freely, a bolus injection of phenylephrine hydrochloride (6 micrograms/kg) was injected in the vein. A sigmoid curve relating systolic blood pressure and heart period was dressed. We analyzed: 1) The gain or sensitivity: the slope of the regression line; 2) The threshold: systolic blood pressure at which the regression begins to be linear. The results were: mean arterial pressure (mmHg): S = 103 +/- 7; PH = 109 +/- 3; gain (ms/mmHg): S = 1.29 +/- 0.10; PH = 0.62 +/- 0.04 (p < 0.001); threshold (mmHg): S = 145 +/- 7; PH = 146 +/- 4. The baroreceptor reflex sensitivity was significantly decreased. No differences appeared in the mean arterial pressure and in the reflex threshold. It is suggested that portal hypertension induces alterations in baroreflex regulation of arterial blood pressure.