This qualitative study analyzed 72 interviews with 39 formerly homeless psychiatric consumers to develop a grounded theory model of engagement and retention in mental health and substance abuse services. Person-centered themes included severity of mental illness and substance abuse (the latter also conflicting with programmatic abstinence requirements). System-related themes inhibiting service use included program rules and restrictions and a lack of one-on-one therapy. Those promoting service use were acts of kindness by staff, pleasant surroundings, and the promise (or attainment) of independent housing. Implications of these findings are discussed in terms of integrating consumers' opinions about services to enhance treatment engagement and retention.