People are fascinated by violent crime, and serial murder may be the most fascinating crime of all. Books, newspapers, television shows, and movies recount the destructive paths of those who kill repeatedly. Many of these accounts leave the impression that serial killers are distinct from other types of criminals and from the public at large. However, current knowledge on serial killers is based almost exclusively on a small number of case studies and a handful of moderately sized archival investigations. Thus, our current level of knowledge on serial murder is, at best, sketchy, and this knowledge may not stand up to more rigorous empirical testing. This entry reviews the definition of serial killing, demographics of serial murder, results of research on serial killers and their ...