OBJECTIVE. We investigated the advantages of using a radiology information system as the primary data source for a mammographic patient-tracking system that is based on a personal-computer local-area network and that requires almost no data entry. HARDWARE AND SOFTWARE. Our mammographic data base is maintained on a file server that provides cross-platform access to both Macintosh and IBM-compatible personal computers. Locally developed software automatically transfers mammographic data from our radiology information system to the file server's mammographic data base. The data transferred include patients' demographics (e.g., hospital identification number, address, referring physician) and the complete mammographic report. With the use of specific terminology, the need for follow-up can be automatically gleaned from the mammographic report and coded within the data base. Graphically oriented, commercially available software provides easy access to this information from any personal computer on our department's network. The software provides considerable flexibility for searching and manipulating the data without the need for customized data-base programming. Redundant data entry and associated errors are drastically reduced, as are personnel requirements for maintaining the system. Relative to most commercial radiology information systems, a personal computer facilitates the steps involved in tracking patients and obtaining highly customized analyses of the mammographic data base. The data in the mammographic data base exactly match those in the hospital's registration data and are easily transferred to other personal-computer programs for ancillary processing. CONCLUSION. This technique is ideal for departments that use a general-purpose radiology information system for mammographic reporting, yet need a more powerful but user-friendly and low-cost method for tracking their mammography patients.