Chronic measurements of systemic arterial blood pressure and heart rate via a chronically implanted telemetric transmitter in unrestrained rats, was validated in a three-phase study. In the first part, week-to-week variability of systolic, diastolic, and mean arterial pressures, and heart rate was found to be minimal over the course of nine weeks. In the second part, the reproducibility of cardiovascular response to three successive administration of sotalol, an antihypertensive agent, was studied. In the last part, cardiovascular parameters determined by telemetry were compared to those obtained by direct arterial catheterization and showed a good linear correlation between those two methods.