The author maintains that technical writers need to consider a variety of information from the field of human factors while producing written instructions and warnings. It is important to consider both the clarity of communication and the discharge of legal duty to warn of potential risks and hazards. The writer must consider the variety of human abilities, the variability of human actions, and the impact that these will have in terms of both use and predictable misuse of a product. The author considers some specific areas of human factors, together with ways in which these may be incorporated into well-designed instructions and warnings. An approach to risk management using estimated benefits and costs is also described.