The chapter distinguishes serial lust killing from other forms of serial killing, such as those motivated by attention-seeking, revenge or material gain. However, it notes that other motivations such as those reflected in mission-killing and ego-boosting can combine with killing motivated by sexual desire. It also distinguishes serial lust killing from mass killing and spree killing. The notion of motivation is key to understanding lust killing as the behaviour is guided by a clear purpose and intention, such as to obtain sexual pleasure by the exertion of dominance over a victim. Most serial lust killers are not judged to be insane and are thereby held accountable by law. The chapter rejects the dichotomies of nature versus nurture and social versus biological, suggesting that such killing can only be understood in terms of a dynamic biology-social interaction. The importance of the acquisition of control is described.