This study examined the rate of admission to public shelters between 1990 and 1992 among persons who received Medicaid-reimbursed inpatient and outpatient psychiatric services and inpatient substance abuse services in Philadelphia between 1985 and 1993. Results show that 7.5 percent of such persons were admitted to public shelters during the three-year period, nearly 2.7 times the rate of shelter use by the general population (2.8 percent). Medicaid recipients treated for serious mental disorders had a three-year rate of shelter use of 8.4 percent. Those receiving inpatient treatment for substance use disorders, including detoxification services, had a three-year rate of shelter admission of 10.2 percent.