During the past two decades, the body of empirical research on warning design and evaluation has grown. Consequently, there are now basic principles and guidelines addressing warning design (e.g., signal words, color, symbols, and text/content), placement (e.g., location within product instructions), and how to enhance the usability of designs by considering factors internal to the user (e.g., beliefs, perceptions of risk, stress). Similarly, evaluation methods have been developed that can be used to measure the effectiveness of warnings such as the degree to which warnings are communicated to recipients and the degree to which they encourage or influence behavioral compliance. An overview of the empirical literature on warning guidelines and evaluation approaches is provided. Researchers, practitioners, and manufacturers can use these guidelines in various contexts to reduce the likelihood that injury and product damage from exposure to a hazard will occur.