OBJECTIVE: This study explored a multifactorial model of vulnerability to homelessness among male veterans of the Vietnam war generation. METHOD: Data from 1,460 male veterans who participated in the National Vietnam Veterans Readjustment Study were used to evaluate hypotheses about the causes of homelessness grouped into four sets of sequential variables: 1) premilitary risk factors, 2) war related and non-war- related traumatic experiences, 3) lack of social support at the time of discharge from military service, and 4) postmilitary psychiatric disorder and social dysfunction. Structural equation modeling was used to explore the posited model of risk factors for homelessness. RESULTS: Postmilitary social isolation, psychiatric disorder, and substance abuse had the strongest direct effects on homelessness, although substantial indirect effects from stressors related to being in the war zone and from premilitary conduct disorder were observed. Several premilitary factors--year of birth, childhood physical or sexual abuse, other childhood traumas, and placement in foster care during childhood-- also had direct effects on homelessness. CONCLUSIONS: Individual vulnerability to homelessness is most likely due to a multiplicity of psychiatric and nonpsychiatric factors, with independent influences emerging at each of four discrete time periods. In view of this complex pattern of influences, prevention efforts directed at individuals must address a very broad range of adjustment problems.Abstract Teaser