This chapter addresses potential barriers to good clinical decision-making, found at all levels of practice. It begins with decision-making at the micro-level-that is, at the level of the individual clinician, who faces a series of decisions with each new case: how to frame problems, what outcomes to pursue, when to stop collecting information, what risks to take, what criteria to use to select practice methods, and how to evaluate progress. The flexible and diverse nature of clinical practice, while allowing for consideration of specific client needs, also leaves room for many kinds of error. These errors can be avoided, or at least minimized, by the use of evidenceinformed assessment practices as outlined in the chapter. At the mezzo-level, requirements of the practice setting (such as mission and funding source) can shape and constrain the way assessment takes place; the media, professional literature, and structure of professional training also exert a powerful influence. Macro-level influences include the widespread medicalization of human behavior; the pharmaceutical companies and managed care institutions comprising the "biomedical industrial complex;" and entities such as the National Institute of Mental Health, the American Psychiatric Association, and the welfare and legal systems. The chapter concludes by urging students to consider the biases that may be inherent in the information on which they base their decisions, as well as how the environment they work in may affect their ability to make sound clinical decisions.