In this study, we compared stenosis severity by quantitative coronary angiography from video and cine images with visual estimation in 14 patients who underwent PTCA. Both cine and video analysis demonstrated a change from 65.2 +/- 2.5 to 36.5 +/- 3.1% diameter stenosis following PTCA, whereas visual estimation (average of three observers) showed improvement from 89.9 +/- 1.7 to 36.0 +/- 3.2%. Percent area stenosis from quantitative angiography showed improvement from 87.9 +/- 1.8 to 56.4 +/- 5.8. These data indicate that visual assessment overestimated percent diameter of severe lesions. To determine if video analysis could provide rapid quantitative assessment of PTCA results, we compared percent diameter and percent area stenosis by video with cine (diameter: correlation coefficient, 0.82; slope, 0.79; area: correlation coefficient, 0.86; slope, 0.83). These results indicate that video-based measurements are not different from cine-derived measurements. Quantitative coronary angiography provides an accurate estimate of changes produced by PTCA and can be performed rapidly and accurately on video images, thus making results available during the PTCA procedure.