The most common techniques currently employed for monitoring blood pressure (BP) in conscious rats and mice are the tail cuff and the exteriorized catheter that feeds a pressure transducer located outside the cage. There are, however, considerable drawbacks associated with these methods, which in many respects make each of these techniques undesirable as an accurate means of obtaining pressure measurements. Recent studies have shown that measurements of physiological variables, such as electrocardiogram (ECG), heart rate (HR), and body temperature (BT), from freely moving rats and mice by using implantable radiotelemetry were more efficient, reliable and less labour intensive when compared to measurement techniques described in the literature so far. Nowadays, measurement of BP by radiotelemetry has been described and validated for many laboratory animal species, including rats and mice. The implantable radiotelemetry technique can circumvent many of the problems associated with conventional methods (tail cuff; exteriorized catheters) of BP monitoring in mice and rats. This chapter describes the surgical aspects of the radiotelemetry techniques currently used to monitor and measure blood pressure in awake animals.