A system was developed to track the centerlines (axes) of human coronary arteries during the cardiac cycle from biplane cineangiograms. The system employs a time interpolation technique on one image plane and a smoothing technique on the other to create simultaneous image pairs. The image pairs are then used to reconstruct the three dimensional axes of the vessels during the cardiac cycle. Once the vessel axes are reconstructed, acceleration, velocity and geometric parameters such as curvature can be obtained. In the present work, a sequence of human angiograms is used to obtain the axial and temporal variation of the curvature of a portion of the left anterior descending coronary artery distal to the third diagonal branch during two cardiac cycles. For the case studied, the change in curvature during the cycle ranged from 0.25 to 1.8 cm(-1), depending upon the position of the site.