OBJECTIVES: Ageing population implies greater demand of hospital services and consequent healthcare costs. This study aims to describe patterns of hospitalization and estimate hospitalization costs for aged patients in public hospitals in the city of Rio de Janeiro, Brazil. METHODS: Retrospective analysis of Rio de Janeiro hospital admissions for elderly people (aged ≥ 60 years) as reported in Brazilian Hospital Information System (SIH/DATASUS) database from January 1st to December 31st 2007. The costs informed in the database represent federal reimbursement values for hospitalizations placed in public hospitals in the city. Admissions were categorized according to ICD-10 groups and age categories. RESULTS: 287,972 hospital admissions were identified for all ages in the city in 2007 and 24.3% were for patients ≥ 60 years (70,077). The five more common reasons for hospitalization were cardiovascular diseases (22.4%), cancer (17.5%), mental and cognitive disorders (11.2%), gastrointestinal (9.3%) and respiratory diseases (7.6%). The in-hospital mortality rate was 14.76% for all causes. When disease groups were analyzed, infectious and respiratory diseases had the higher mortality rates (38.6% and 38.3%, respectively). The mean length of stay was 14.3 days and the average cost for elderly patients hospitalizations was 960,62 BRL. The total amount paid for hospitalization of elderly patients in 2007 was 67,317,348 BRL, 30.7% of all hospitalization costs. CONCLUSIONS: The findings showed the significant contribution of the elderly to public hospital expenditures with leading causes of admission including cardiovascular diseases, cancer and mental and cognitive disorders. Additionally, the higher in-hospital mortality rate was seen for preventable diseases. These results reinforce the need of prevention strategies among the elder population for targeted conditions.