Information systems for family practice are vital in its development as an academic discipline, in the teaching and learning process which ultimately improves the quality of care, and in the planning processes which must be used to rationalize the distribution of scarce resources in the health-care field. The provision of sufficient data for these purposes demands a flexible system, generally one based on the computer as a data storing and analyzing tool. Such a system has been developed in the teaching practices of the Department of Family Medicine, University of Western Ontario; the methods employed and the uses for that system are to be described in a series of four papers. This first paper describes the methods developed for gathering demographic information on the practice population.