Research issues concerning human interaction with computers have become crucial because of dramatic increases in the number of computer users who have no formal mathematical, engineering, or computer science training. This review focuses on the state of the art in Software Psychology--the study of human factors in computer systems. One area of software psychology, the psychology of programming, is picked for an in-depth discussion of research results. This area was selected for its interest to the readers of the PROCEEDINGS OF THE IEEE. The review then discusses the methodological issues involved in performing experimental research in software psychology. Future trends are discussed both for the programming research reviewed here and for the whole field of software psychology. The conclusions identify multidisciplinary training and research as critical to further progress in this field.