Background: Among case mix classifications, the best for hospitalized elders is the Resource Utilization Groups (RUG) system, which allows a better location of patients, resource administration and the design of health care strategies for elderly people. Aim: To report the results of RUG-T18 classification of elderly patients admitted to an university hospital. Patients and methods: RUG-T18 classification was applied to 210 patients aged 75.2 ± 7.2 years old, 108 male, admitted to the Clinical Hospital of the Catholic University of Chile. Results: The clinical classification of assessed patients was rehabilitation in 50.9% of cases, special care in 10.5%, clinically complex in 37.1% and reduced physical functions in 0.5%. None had behavioral alterations. There were no differences between subjects older or younger than 75 years old. Daily life activities showed that help was required for sphincter control in 46% of patients, for feeding in 44% and for mobilization in 64% (28% of patients required help from two or more people). Geriatric assessment showed that, since 1993, the proportion of elders with greater functional derangement increased from 18 to 28%, and the proportion of those with mental disturbances from 4 to 12%, specially among those over 75 years old. Conclusions: Most elders admitted to the hospital are classified in the superior categories of the RUG-T18 system and have severe mental and functional limitations. These patients require a multidisciplinary approach with a great emphasis in rehabilitation.