There is substantial evidence from the developed world that health care provision is an industry that frequently, and, avoidably, harms vulnerable people. Over the last decade, the awareness of policy makers and health professionals about patient safety has been raised in many countries all over the world through important reports proposing recommendations for improvement.In spite of the relatively low dispensing error rates further improvements in pharmacy distribution systems are still important because pharmacies dispense such high volumes of medications that even a low error rate can translate into a large number of errors. Human error is inevitable, and organizational risk management experts have proposed the deployment of robust defense systems in the dispensing process.This monograph, reports on three separate but related dispensing error studies aimed at evaluating some of the potential causes of errors and error defense operations in the dispensing process in selected UKhospitals.