Pressure waveform fidelity was examined in two sizes of the Bard catheter introducer. The purpose of this endeavor was to determine whether accurate blood pressure measurements could be achieved directly via the catheter introducers. The introducers were incorporated into a mock circulatory system for the study. The effects of supporting dilators and catheters within the introducer sheath during pressure measurements were also considered. Parameters used to explain pressure waveform response within the catheter introducers included the damping coefficient and the natural frequency of the catheter introducer, and the effects of impedance mismatching between the transducer and the mock circulatory system. Overall, the pressure measurements obtained from the catheter introducer were distorted. Mean pressure levels measured in the introducers were up to 15 mmHg higher than the true mean pressure. The distortion in the pressure measurements can be attributed for the most part to impedance mismatching. In sum, the pressure measurements obtained from catheter introducer-manometer systems should be used only referentially, and not as an absolute standard.