• The interaction of congenital and postnatal antecedents of criminality was studied in 862 Swedish men adopted at an early age by nonrelatives. Most explained variability was due to differences between the genetic predispositions of the adoptees, but substantial contributions were also made by postnatal environment, either alone or in combination with specific genetic subtypes. There was no overlap between the congenital antecedents of alcoholism and nonalcoholic criminality, but some postnatal variables were common to criminality and one type of alcoholism that is limited to expression in men, according to earlier studies. Low social status alone was not sufficient to lead to criminality, but did increase risk in combination with specific types of genetic predisposition. Unstable preadoptive placements contributed to the risks of both petty criminality and malelimited alcoholism, but not to other types of alcohol abuse. We discuss these results in terms of their clinical and social implications.