Many nuclear power plants are modernizing with digital instrumentation and control systems and computer-based human-system interfaces (HSIs). The purpose of this paper is to summarize the human factors engineering (HFE) activities that can help to ensure that the design meets personnel needs. HFE activities should be integrated into the design process as a regular part of the engineering effort of a plant modification. The HFE activities will help ensure that human performance issues are addressed, that new technology supports task performance, and that the HSIs are designed in a manner that is compatible with human physiological, cognitive and social characteristics.