An 80386 PC-based system was designed to track automatically multiple, miniature radiopaque markers implanted in the heart wall. This system eliminated the need for tedious, time-consuming manual digitization of marker coordinates. Use of a MATROX MVP-AT/NP image processing board incorporated advanced image processing and graphics features into the low-cost PC environment. Digital image enhancement and segmentation techniques (such as limiting analysis to predefined windows of interest, spatial band-pass and matched filtering, contrast stretching and clipping, linear adaptive prediction, intensity histogram analysis, adaptive binary thresholding, region growing, expanding region of analysis, and feature extraction) were incorporated into a user-friendly integrated marker processing software environment. Improved speed, accuracy, and reproducibility of the marker digitizing process were realized. These basic techniques have broad applications to other image processing needs in biomedical research.