Knowledge on the characteristics of patients admitted to psychiatric hospitals is essential to adequate care, yet such information is not always available. A survey was conducted on patients in the 20 psychiatric hospitals in the city of Rio de Janeiro, Brazil. This paper presents demographic and socioeconomic data on the study population: 3223 persons (66.0% male; 52.6% under 40) on October 24, 1995. 73.8% had not finished elementary school; 25.5% were illiterate. 71.6% of the males and 61.1% of the females were single. Both groups had the same divorce percentage (13%). 43.1% of patients had jobs at the time of first admission, but only half had kept them by the time of this survey. Some 50% of the patients only received visits at extended intervals or not at all. This finding, plus the fact that 37.4% had been hospitalized for more than one year and 65.1% did not leave the hospital during holidays or weekends, provides a picture of their social isolation. The findings are discussed based on epidemiological data, and hypotheses are suggested to explain some of the results.