OBJECTIVE: This study examined the relationship between childhood experience and homelessness in psychiatric patients. METHOD: Three large and diverse samples of homeless patients (N = 512) were compared with a sample of patients who had never been homeless (N = 271), with respect to childhood experience of foster care, group home placement, and running away. One of the homeless samples and the never homeless sample were drawn from patients admitted to a state mental hospital. In this state hospital population, risk ratios for lifetime prevalence of homelessness could be derived. RESULTS: In the three homeless samples, over 15% had a history of foster care, over 10% had a history of group home placement, and over 20% had a history of running away. These figures compared with 2%, 1%, and 5%, respectively, in the never homeless sample. In the state hospital, the lifetime prevalence of homelessness in patients with any one of these childhood experiences was about threefold that of other patients. A history of homelessness was reported by the great majority of state hospital patients who had had one of these childhood experiences. CONCLUSIONS: These childhood experiences were strongly associated with adult homelessness in these psychiatric patients. It might be possible to prevent homelessness in some cases by interventions aimed at patients with such childhood histories.