Digital analysis of cine film provides numerous options for altering images by frame averaging or filtering algorithms that either smooth or enhance edges. While these may subjectively enhance image quality, there is no uniformity in their use among laboratories and effects on quantitative coronary analysis may not be ideal. To determine which processing algorithms might help or hinder quantitative coronary arteriography, cine film images of precision drilled stenotic cylinders (0.83 to 1.83 nm diameter) implanted in dog coronary arteries were analyzed with and without such algorithms. Video frame averaging of 1 to 49 frames had no effect on measures of accuracy (mean differences) but precision (standard deviation of mean differences) was improved from 0.23 to 0.17 mm (p less than 0.05) with video averaging of greater than or equal to 25 frames. Edge enhancement filtering algorithms resulted in slight deterioration of accuracy and precision and smoothing filtering algorithms caused modest improvements in these parameters; however, these changes were not significantly different from unprocessed images. Using edge enhancement filtering algorithms, accuracy was significantly worse (-0.27 mm) compared to a smoothing filter enhancement algorithm (-0.08 mm, p less than 0.001). The combination of video averaging and smoothing algorithms had no additional beneficial effects. Thus, precision of quantitative coronary analysis of cine film can be optimized by appropriate video averaging. Edge enhancement filtering algorithms should be avoided whereas smoothing filter enhancement algorithms may improve accuracy.