Ensuring patient safety is essential for better heath care. Safety have gripped public attention ever since the release of the report "To Err is Human". To find strategies of promotion of patient safety has stimulated models that improve knowledge of adverse events. Adverse drug events are the most common cause of injury to hospitalized patients and are often preventable. Many tactics are available to make system changes to reduce errors and adverse events; they fall into five categories: Reduce complexity, optimise information processing, automate wisely, use constraints, and mitigate the unwanted side effects of change. These tactics can be deployed to support any of the three strategic components of error prevention, detection, and mitigation. Although progress has been slow, the pace of change is likely to accelerate, particularly in implementation of electronic health records and diffusion of safe practices.