Sexual homicide refers to murders that involve a sexual component in the crime. Definitions of serial murder differ according to the number of murders that constitute it and the time frame within which the murders occur. Serial murder must also be distinguished from mass murder (the killing of a number of people at one site) and "spree" murder (the killing of two or more murders at separate locations with no cooling-off period between murders. Serial murders may or may not be sexual homicides. The most notable classification system to date for serial murder and sexual homicide was developed by Ressler and colleagues (1988). They defined four categories of sexual homicide: organized, disorganized, mixed, and sadistic. The review of historical background encompasses historical case examples and the evolution of FBI research on serial and sexual killers. Following an overview of epidemiology, a discussion of offender characteristics addresses general offender and victim findings, organized versus disorganized crime, mobility classification of serial murderers, social background characteristics, etiology, and the role of fantasy. The discussion of assessment and diagnosis addresses diagnostic issues and findings and diagnoses in juvenile sexual homicide offenders. Topics considered in the examination of clinical management and treatment include the insanity defense, the National Center for the Analysis of Violent Crime, investigative profiling, and community issues. 73 references