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% 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.