For the purposes of this study, a "drug" includes prescription drugs and biologics, excluding blood and blood products and tissues for transplantation. The objectives of the study are: To develop a fuller understanding of drug safety and quality issues through the conduct of an evidence-based review of the literature, case studies and analysis. This review will consider the nature and causes of medication errors; their impact on patients; and the differences in causation, impact and prevention across multiple dimensions of health care delivery including patient populations, care settings, clinicians, and institutional cultures