It can be theorized that loneliness plays a significant role in the development and continuation of violent, antisocial attitudes and behavior. Analysis of case reports of two serial killers, Dennis Nilsen and Jeffrey Dahmer, indicate that there is evidence for such a link. In this article, a list of significant correlates of loneliness and antisocial behavior is presented. This may be useful for the assessment of possible dangerousness and in the development of prevention and intervention programs. Suggestions are made for the adequate treatment of loneliness and correlated violent, antisocial behavior. A need is recognized for more research into the psychosocial, emotional, neurobiological, cultural, and ethnic determinants of loneliness and their correlation to specific antisocial and/or criminal behavior.