This analysis examined the impact of permanent supportive housing on the use of acute care public health services by homeless people with mental illness, substance use disorder, and other disabilities. This study found that eighty-one percent of residents remained in permanent supportive housing for at least one year. Housing placement significantly reduced the percentage of residents with an emergency department visit (53 to 37 percent), the average number of visits per person (1.94 to .86), and the total number of emergency department visits (56 percent decrease, from 457 to 202) for the sample as a whole. Providing permanent supportive housing to homeless people with psychiatric and substance use disorders reduced their use of costly hospital emergency department and inpatient services, which are publicly provided. (Authors)