Previous studies have shown that comprehensive geriatric assessment and follow-up can improve the health of hospitalized elderly patients. To evaluate the effectiveness of consultative geriatric assessment and limited follow-up for ambulatory patients, we randomized 600 elderly patients who were enrolled in a health maintenance organization into three groups: (1) consultation by a geriatric assessment team, (2) consultation by a "second opinion" internist, and (3) only traditional health maintenance organization services (control patients). The geriatric assessment team identified previously unrecognized problems in 35% of patients and advised changes in medication regimens for more than 40%. Nevertheless, patients who received assessment achieved only a small benefit in cognitive function after 3 months, which was not sustained for 1 year. There was no difference among groups in other measures of health status. Consultative geriatric assessment with limited follow-up did not benefit most older ambulatory patients in a health maintenance organization; if such care can be used effectively for ambulatory patients, it will require either additional targeting or continuing care or both.