526 Mental health services research provides a critical bridge between efficacy demonstrated in randomized controlled trials and treatment effectiveness in real-world settings. It does so by taking into account multiple influences—for example, characteristics of service systems, consumers, and providers—that influence the effectiveness of treatments in service delivery settings (1). One way to understand the impact of these multiple influences is by developing a program theory (2,3) or heuristic model (1) to guide an effectiveness evaluation from inception to interpretation. The heuristic model proposed by Shern and Evans (1) provides a framework for guiding mental health services research by identifying five domains that affect both consumer and service outcomes: consumer characteristics, such as demographic characteristics, clinical status, and functional status; organizational characteristics, such as rules that govern behavior in an organization; practitioner behavior, such as prescribing, and practitioner characteristics, including training, values, beliefs, and therapeutic orientation; services environment, such as attitudes, values, and beliefs of staff; and service system characteristics, such as external laws and regulations influencing service delivery and reimbursement. From the perspective of this heuristic model, we discuss the implications that the findings of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) have for monitoring and influencing the behavior of prescribers through changes in the service system that should have an impact on both consumer outcomes (for example, change in clinical status or side effect burden) and system outcomes (for example, changes in resources devoted to different prescribing patterns).