A practical usability engineering process that can be incorporated into the software product development process to ensure the usability of interactive computer products is presented. It is shown that the most basic elements in the usability engineering model are empirical user testing and prototyping, combined with iterative design. Usability activities are presented for three main phases of a software project: before, during, and after product design and implementation. Some of the recommended methods are not really single steps but should be used throughout the development process. >