Measurement of arterial blood pressure in experimental animals is a cornerstone of basic research in hypertension. There are two principal types of measurement techniques: direct and indirect. Each of these methods has advantages and disadvantages, and it is incumbent upon the investigator to choose the method that will provide the most accurate and reliable information based on the experimental design. The purpose of this chapter is to provide the reader with a description of the more common and useful methods for the measurement of arterial blood pressure. The emphasis will be on methods applicable to the rat and dog, since these are the most commonly used species in cardiovascular research. The salient aspects comparing the various methodologies will be addressed; however, a detailed comparison of the accuracy and reliability of specific types of direct and indirect methodologies will not be discussed. The reader is encouraged to peruse the excellent reviews by Bunag 1-2 and Raftery 3 for this information. The chapter will address the general aspects of direct and indirect measurement of arterial pressure, and then will proceed into specific uses of these techniques in various animal species.