Background: Elderly people (>60 years) in Chile represented 11.4% (n=1.717.478) of the total population in 2002. The group with disabilities or mental problems is increasing and there is no reliable information about the number of institutionalized elderly subjects. Aim: To estimate the number of elderly people living in residences for long term care and their and main characteristics. Patients and methods: Chilean Census does not provide exact information about institutional care, therefore we developed a «proxy» indicator of the percentage of institutionalized elderly (those living in «collective residences with more than 5 elderly persons and in which they represent more than 25% of the residents». This proxy has a R2=0.9859 with the true value of institutionalized persons for those Latin-American countries with exact value in census data at CELADE. Results: Using the proxy we found that institutionalized elderly population had increased from 14,114 (1992) to 26,854 (2002) and is projected to reach 83,500 (2025). In 2002, there were 1.668 institutions (37.4% informal care). In the Metropolitan Area, there were 804 institutions (14.178 elderly persons) and 40.3% of these were registered at the Ministry of Health. The proportion of institutionalized elderly subjects was 1.56% of the total elderly population; this proportion increased from 0.87% in subjects 60-74 years old to 2.5% among subjects aged 75-84 years and 6.1% in subjects 85 years old and over. Among subjects living in institutions, 60.9 were women, 21% were married, 35% were single, approximately 50% receive a pension and around 15% were handicapped. Conclusions: Institutional care affects a small percentage of elderly population, but it will increase in the near future. The main characteristics of institutionalized elderly subjects are not well known. We propose to create a formal Registry of these institutions and to include Nursing Homes and hospitals in type of housing of future Censuses (Rev Méd Chile 2004; 132: 832-8)