Every level of analysis of biological factors - from molecular genetics, to brain structure and function, to neuropsychological performance - has found links between biology and antisocial behavior. Likewise, a number of social or environmental factors - maltreatment, socioeconomic status, education, and so on - are believed to contribute to crime and aggression. Over the past two decades, increasing interest in the interaction between biological and social factors in various behaviors and disorders has led to several fruitful lines of research. A great deal of such research has supported the interacting roles of nature and nurture in the development of criminality. This chapter will provide an overview of some of the major biosocial findings in research on crime and antisocial behavior.