The purpose of this study is to identify differences between older and younger homeless subgroups. Nine hundred homeless persons were interviewed using the National Institute of Mental Health Diagnostic Interview Schedule, and DSM-III-R diagnoses were made. Results showed that 79 (13%) of the 600 men and 10 (3%) of the 300 women were in the older (age > or = 50 years) group. Compared with their younger counterparts, older subjects were more likely to be male and white, to report lower incomes and poorer health, and to meet criteria for lifetime alcohol-use disorder. Fewer older than younger subjects met criteria for lifetime drug use disorder and post-traumatic stress disorder. These findings suggest that older and younger individuals have different vulnerabilities to homelessness.