Over the past 35 years, information technology has permeated every business activity. This growing use of information technology promised an unprecedented increase in end-user productivity. Yet this promise is unfulfilled, due primarily to a lack of understanding of end-user behavior. End-user productivity is tied directly to functionality and ease of learning and use. Furthermore, system designers lack the necessary guidance and tools to apply effectively what is known about human-computer interaction (HCI) during systems design. Software developers need to expand their focus beyond functional requirements to include the behavioral needs of users. Only when system functions fit actual work and the system is easy to learn and use will the system be adopted by office workers and business professionals. The large, interdisciplinary body of research literature suggest HCI's importance as well as its complexity. This article is the product of an extensive effort to integrate the diverse body of HCI literature into a comprehensible framework that provides guidance to system designers, HCI design is divided into three major divisions: system model, action language, and presentation language. The system model is a conceptual depiction of system objects and functions. The basic premise is that the selection of a good system model provides direction for designing action and presentation languages that determine the system's look and feel. Major design recommendations in each division are identified along with current research trends and future research issues.