This article summarizes Canadian research in "dual diagnosis" spanning the past 20 years and places this research within a historical and policy context. Canadian researchers have made important contributions with regard to understanding inpatient and outpatient mental health services, families, autism, specific disorders and behaviors, aboriginal mental health, forensics, and emergencies. In this article, we aim to summarize several of these contributions. Following a summary of recent research findings, we offer some suggestions and directions for future research in our country.