Pressure sensors in biomedical applications are very important because they provide data that may be used to assess physiological function, diagnose disease, and provide for appropriate treatment regimens. Pressure sensors have a large number of applications in biomedicine, in particular, for the measurement of interface pressures and internal pressures. The interface pressures can be measured using conductive polymer pressure sensors, semiconductor strain gauges, metal strain gauges, capacitive pressure sensors, and optoelectronic pressure sensors. Internal pressures can be measured, using the needle manometer method, the Wick catheter method, integrated circuit implantable sensors, and fiber-optic catheters. The packaging materials of internal pressure sensors are manufactured from biocompatible covering materials to avoid tissue infection and change in sensor characteristics over time. The first section of the chapter outlines the general forms of pressure measurement systems and their characteristics, including performance, accuracy, loading effects, noise, and reliability, which is followed by a detailed summary of instruments and measurement systems in biomedical applications for specific types of pressure measurements. The final section presents the theory behind the components used to form the measurement systems, in particular, the pressure-sensing elements, transduction.