PURPOSE To evaluate the accuracy of a new non-invasive method (Vasotrac) to measure blood pressure (BP) with accompanying arterial wave-form and pulse-rate display when compared with BP and waveform measured invasively. METHODS Healthy volunteers (n=53) served as subjects for the study. Blood pressures and waveforms obtained via a radial artery catheter (IABP) were compared with non-invasive measurements obtained every 12-15 beats by the new system (Vasotrac BP) from the opposite radial artery. In a sub-group of volunteers (n=11), BP was acutely increased and decreased with isoproterenol, phenylephrine and sodium nitroprusside. Data were analyzed by determining correlation and agreement between the two systems of measurement. Waveforms obtained by the two systems were qualitatively examined. RESULTS Non-invasive BP measured every 12-15 beats by the Vasotrac correlated with IABP (systolic r2 = 0.89; diastolic r2 = 0.88; mean r2 = 0.94). The actual values obtained by the two methods agreed closely with > 90% of readings being within 2SDs when plotted by the Bland Altman method. This was also true during vasoactive drug infusion when BP changed acutely and swiftly. During this dynamic period, Vasotrac BP accurately tracked the changes in IABP with correlations (systolic r2 = 0.82; diastolic r2 = 0.89; mean r2 = 0.95) and close agreement (> 90% of readings were within 2 SDs in the Bland Altman plot). Waveforms displayed by the two systems were qualitatively very similar. Pulse rates measured by the two systems were identical. CONCLUSIONS The Vasotrac system displayed an arterial waveform which was similar to that obtained directly and measured BP and pulse rate accurately. It should be a convenient device to measure BP continually in a non-invasive fashion.