A serial killer is someone who has instigated and participated in at least three unlawful and unilateral murders over an indeterminate time span, with a clear cooling-off period separating each one. Serial murderers cannot be agents of the state, or act on anyone else’s behalf. A succession of linked homicides of any sort is an exceptionally rare form of human criminality. In the United States, serial killers are currently responsible for about 800 deaths annually. Serial killers have become an omnipresent theme in many advanced consumer societies. The United States and its cultural satellites seem most affected: the United Kingdom, Germany, France, Australia, Russia, Japan, and Canada. There is a much lower incidence in the Netherlands, Korea, Sweden, Ireland, New Zealand, Italy, and Switzerland. The more affected areas share certain conditions that do not afflict the other groups: significant counter-culture, high prison population, post-imperial heritage, densely populated urban communities, ongoing socioeconomic transformation, and great expectations of consumerism. In the United States, lust-driven serial killers tend to be born in Michigan but to kill in California. Sexual serial killers are often ambitious, dominant, intelligent individuals. Repeated carnal homicide may be their means of exacting revenge against society and of making a name for themselves. The number of serial killers varied considerably from State to State during the years 1860 to 1995. There is a credible homicidal proclivity between the State of Wisconsin and cannibalism. Another particular kind of homicidal activity connected with a certain State might be the abundance of bizarre, motiveless serial murders in California. There are no comprehensive explanations for disparities in the regional prevalence of both serial killers and their killings. Finding the common predisposing characteristics of the high and low frequency States may require the development of a new hybrid discipline, which might be termed psycho-epidemiology. 4 figures, 1 note, 18 references