A review of the history of the term "serial murder" shows that it originated and persisted in the literature long before the 1980's. Recognition of the phenomenon of serial murderers is centuries old, even if there was no distinct term that was generally accepted for this type of criminal behavior. In the current literature, serial murder has been defined with a wide range of variables. Some definitions are based on characteristics of the offenders. Others delineate specific aspects of the offenses; however, there is apparently a consensus on the following points: serial murder involves the killing of a number of people over a period of time by the same person. The length of time and the number of victims necessary for a homicidal pattern to qualify as serial murder is open to debate. Regarding the element of time, the essential point of distinction is that the killings occur as discrete events over an extended period of time, rather than as part of a more limited crime spree. Regarding the minimum number of victims, it would be reasonable to stipulate a minimum of three victims, which have been documented through established links by forensic evidence, whether prosecuted or not. Specifying a minimum number is necessary in maximizing the reliability of data on serial murder. Regarding motive, this paper proposes that the hallmark of the serial killer is his motivation to kill repeatedly for personal gratification, regardless of the context in which killings are committed. Thus, the author recommends that "serial murder" be defined as "three or more forensically linked murders committed as discrete events by the same person(s) over an extended period of time and where the primary motive is personal gratification." 46 references and 4 footnotes