To understand the psychology of sexual versus nonsexual serial homicide, we begin by considering the complexity in identifying and understanding the sexual element in homicide offenses and how, consequently, there is significant heterogeneity in the cases classified as sexual. While sexual serial homicide cases necessarily have in common some kind of sexual behavior within their modus operandi, there is no paradigmatic psychological profile that can be contrasted with nonsexual serial homicide, which itself refers to various types of violent offending. Therefore, this chapter aims toward an understanding of sexual serial homicide as a subcategory of sexual offending in terms of its uniqueness compared to other subcategorizations of sexual violence, particularly non-serial sexual homicide, rather than by direct comparison to nonsexual serial homicide. The latter is explored in detail throughout the volume. Thus, this chapter will define, examine, and compare nonsexual homicide, sexual nonserial homicide, and sexual serial homicide, in order to clarify what characterizes sexual serial homicide. Critical considerations in the study of sexual homicide, risk assessment and treatment, and ultimately, prevention of such types of offense are discussed.