Subjects were 5,182 Danish males for whom conviction data were found. Subjects ranged in age from 29 to 52 years old at the time of data collection. Conviction data were obtained from court records; mental illness was assessed from admission/discharged data maintained by the Institut for Psykiatrisk Demografi. Differential analyses of data were conducted to permit estimation of size effects. Results show that parental psychiatric illness contributed significantly to offspring criminal behavior, especially in interaction with parental criminal behavior. Multiple recidivistic and violent offending were characteristic of the subjects' biological backgrounds. The relationship of parental psychiatric illness with sons' violence was found to be violence-specific. Parental diagnoses of drug/alcohol abuse and personality disorder contributed most strongly to adoptee criminal outcomes, while parental psychoses did relate to offspring criminal factors. The heritable factors associated with these antisocial diagnostic types are probably distinct from those which account for the previously reported genetic association between parental and offspring criminality. The importance of the mental illness/crime genetic relationship is discussed in terms of societal costs. Tabular data and 134 references are included. (Author abstract modified)