The purpose of this study was to determine the accuracy of imaging small coronary arteries with current radiographic equipment. Phantom assessments were performed using a phantom that comprises a large array of circular objects of varying diameter and contrast density. More objects could be identified in the moving cinearteriogram than in single cine frames. Using the largest object as the calibration standard, diameters less than 1 mm were markedly overestimated. A simple morphometric method showed that arteriographic visualization of small vessels was better by digital processing than by cine recording. However, there was no statistically significant difference in the average size of the smallest identifiable vessel by either method (0.5 versus 0.51 mm). After correcting for overestimation and the inaccurate imaging of the smallest detectable vessels, the practical arteriographic threshold is approximately 0.5 mm. Parametric imaging holds promise, but its significance for evaluating small vessel disease has yet to be determined.