Previous research suggests that former psychiatric hospital patients become homeless due to (1) their inability to make use of treatment services, (2) the lack of available services, or (3) the lack of available tangible economic supports. However, supportive studies tend to examine the homeless in isolation and therefore do not fully determine whether the three factors differentiate those former patients who become homeless from the large group who do not. They also fail to undertake multivariate analysis that can separate determinants from factors that are only spuriously related to the lack of a domicile. The current study thus compares homeless and other domiciled but vulnerable former psychiatric patients within a multivariate framework. Results suggest that, except for age, few measures representing the inability to use services or the lack of treatment services predict homelessness. In contrast, homelessness is related to traits that reflect the lack of tangible resources, including the lack of Supplemental Security Income (SSI), the lack of other income maintenance benefits, and the lack of work income. Such results suggest that homelessness might be avoided if vulnerable former patients receive special but not traditional types of care, if young people are retained in treatment, and if the vulnerable receive help in obtaining material support. Copyright © 1991 Wiley Periodicals, Inc., A Wiley Company