With a decline in the proportion of medical students pursuing family practice careers, it is necessary to better understand the factors influencing their career decisions. The Fishbein model of attitude formation was used as a framework for developing a questionnaire to measure students' attitudes toward a career in family practice and the social support students perceived they had for that career. The questionnaire was administered to fourth-year-medical students a short time before residency match day. Both the attitude and social support scales had excellent psychometric characteristics. The usefulness of these scales in discriminating between career choices of family practice and other clinical careers was tested. The social support scale did not discriminate well, whereas the attitude scale discriminated quite well. The students who chose careers in family practice differed from students who chose other careers in 14 of 19 values about characteristics of family practice but differed from them in only two of 19 beliefs about family practice. The implications for advising medical students about careers in family practice are discussed.