Previous reports have examined separately the role of perinatal biology in the etiology of violent criminal behavior and the etiology of antisocial personality disorder (ASP). This paper brings together those two studies to test the hypothesis that violent behavior and ASP may result from different etiological factors. The two studies are on Danish birth cohorts, examined both for perinatal health and for violent, aggressive, and antisocial behavior later in life. Results suggest that while perinatal factors may be important in the etiology of violent criminal behavior, they do not appear to be similarly influential in the formation of ASP. These two studies are examined and their results and findings discussed in light of the limited literature in this area.