A 14-item, self-administered, multidimensional, functional social support questionnaire was designed and evaluated on 401 patients attending a family medicine clinic. Patients were selected from randomized time-frame sampling blocks during regular office hours. The population was predominantly white, female, married, and under age 45. Eleven items remained after test-retest reliability was assessed over a 1- to 4-week follow-up period. Factor analysis and item remainder analysis reduced the remaining 11 items to a brief and easy-to-complete two-scale, eight-item functional social support instrument. Construct validity, concurrent validity, and discriminant validity are demonstrated for the two scales (confidant support--five items and affective support--three items). Factor analysis and correlations with other measures of social support suggest that the three remaining items (visits, instrumental support, and praise) are distinct entities that may need further study.