Medical practice is increasingly using medical electrical equipment for observation and treatment of patients. use errors caused by inadequate medical electrical equipment usability have become an increasing cause for concern. The usability engineering process is intended to achieve reasonable usability, which in turn is intended to minimise use errors and to minimise use associated risks. Some, but not all, forms of incorrect use are amenable to control by the manufacturer. The usability engineering process is part of the process of risk control. This Collateral Standard describes a usability engineering process, and provides guidance on how to implement and execute the process to provide medical electrical equipment safety. It addresses normal use and use errors but excludes abnormal use.