Although these data are preliminary, they show that severely mentally ill homeless patients who were offered an assertive community outreach approach with comprehensive services were largely able to adhere to treatment recommendations in most domains except for daily structure. Patients were least compliant in the domain of daily structure, suggesting the importance of low-demand housing and drop-in centers for these individuals.The correlation of noncompliance in the domain of substance abuse with noncompliance in other domains underlines the importance of developing innovative approaches to substance abuse in this population.Poorer housing outcomes were particularly associated with noncompliance in the domains of both housing and daily structure. Patients' compliance with housing recommendations and their housing outcome were linked. However, the need for daily structure, or something to do all day, was also related to poor housing outcomes and clearly needs to be addressed in this population. A greater understanding of compliance patterns is clearly necessary to create more effective programs and services for homeless mentally ill persons.