Errors are an inevitable part of the performance of any task relying on human cognition and performance. While errors in medicine are no less common than other industries, there is a culture of infallibility in medicine that denies the true prevalence of errors. Increasingly the recognition of errors and their role in patient care is becoming a more prominent topic for discussion among medical practitioners. This lecture reviews some of the common causes and effects of errors, while providing a strategic framework for addressing and mitigating medical errors. This lecture provides a general overview of medical errors, including diagnostic errors with a focus on those related most closely to anesthesia. A systems based approach that recognizes weak links in the care cascade will be used to discuss how through the adoption of tools (ie. checklists, proper drug labelling etc) and using tested designs (i.e. alarms, standard safety equipment etc.) many of the most common errors involving anesthesia can be lessened.