Homicide–suicide is the phenomenon in which an individual kills 1 or more people and commits suicide. Research on homicide–suicide has been hampered by a lack of an accepted classification scheme and reliance on media reports. Mass murder–suicide is gaining increasing attention particularly in the United States. This article reviews the research and literature on homicide–suicide, proposing a standard classification scheme. Preventive methods are discussed and sociocultural factors explored. For a more accurate and complete understanding of homicide–suicide, it is argued that future research should use the full psychological autopsy approach, to include collateral interviews.