BACKGROUND AND METHODS. The prevention of disability in elderly people poses a challenge for health care and social services. We conducted a three-year, randomized, controlled trial of the effect of annual in-home comprehensive geriatric assessment and follow-up for people living in the community who were 75 years of age or older. The 215 people in the intervention group were seen at home by gerontologic nurse practitioners who, in collaboration with geriatricians, evaluated problems and risk factors for disability, gave specific recommendations, and provided health education. The 199 people in the control group received their regular medical care. The main outcome measures were the prevention of disability, defined as the need for assistance in performing the basic activities of daily living (bathing, dressing, feeding, grooming, transferring from bed to chair, and moving around inside the house) or the instrumental activities of daily living (e.g., cooking, handling finances and medication, housekeeping, and shopping), and the prevention of nursing home admissions. RESULTS. At three years, 20 people in the intervention group (12 percent of 170 surviving participants) and 32 in the control group (22 percent of 147 surviving participants) required assistance in performing the basic activities of daily living (adjusted odds ratio, 0.4; 95 percent confidence interval, 0.2 to 0.8; P = 0.02). The number of persons who were dependent on assistance in performing the instrumental activities of daily living but not the basic activities did not differ significantly between the two groups. Nine people in the intervention group (4 percent) and 20 in the control group (10 percent) were permanently admitted to nursing homes (P = 0.02). Acute care hospital admissions and short-term nursing home admissions did not differ significantly between the two groups. In the second and third years of the study, there were significantly more visits to physicians among the participants in the intervention group than among those in the control group (mean number of visits per month, 1.41 in year 2 and 1.27 in year 3 in the intervention group, as compared with 1.11 and 0.92 visits, respectively, in the control group; P = 0.007 and P = 0.001, respectively). The cost of the intervention for each year of disability-free life gained was about $46,000. CONCLUSIONS. A program of in-home comprehensive geriatric assessments can delay the development of disability and reduce permanent nursing home stays among elderly people living at home.