Psychological research done in Canada and relevant to the treatment of persons institutionalized in psychiatric and correctional settings is reviewed. Studies are divided into four categories: prevention, assessment, treatment, and release. Although some innovative and influential applied research has been accomplished, the amount of applied research is relatively small and tends to focus on assessment rather than treatment issues. A discussion of some of the factors responsible for the relative paucity of relevant research is followed by a discussion of what might be done to improve the quantity and quality of research efforts in the future. Rule and Adair (1984) recently summarized the substantial contributions of psychology as a social science to Canadian society. In that paper, contributions by psychologists to the treatment of the mentally ill or to correctional populations were not reviewed. The present paper is a summary of research completed by psychologists in Canada that is relevant to the treatment of persons institutionalized in psychiatric and correctional settings. We have chosen to limit the scope of the paper to studies that have had fairly direct applications and studies in which possible applications are mentioned. Although we have attempted to identify, or at least sample, all of the Canadian research that meets these criteria, our coverage of more recent material is better than that of older, and our coverage of material published in French is very poor.The paper begins with a review of relevant papers. Papers are divided into four categories: prevention, assessment, treatment, and release. Following the review is a discussion of some of the factors responsible for the relative paucity of relevant research, and a discussion of what might be done to improve the situation in the future.Thanks are due to G. Harris for helpful comments on an earlier draft of this paper, and to R. Berry, W.R.N. Blair, P. Gendreau, J. Pettifor, and many others for providing much helpful material. Apologies are due to many people, especially those who publish in French, whose work did not come to our attention.