The Department of Family Medicine and Practice at the University of Wisconsin-Madison has devised and implemented an alpha-numeric system of identifying patient records together with a system of chart filing based on a variation of terminal digit filing. The system provides each patient with a unique identification number. This permanently assigned number is used as part of the medical record (chart) information, as the basis for assigning an account number, as the basis for determining the storage location of the chart in the record room, and as the basis for a family identification number. The number defines the patient's sex and position within the family, and its permanency ensures a capability for conducting both short- and long-term ambulatory care research in the family context.