Results indicate a significant relationship between criminal convictions of biological parents and their adopted offspring. The relationship is particularly strong for offenders, both parent and adoptee. No evidence was found for a relationship between the type of parent and adoptee convictions. A number of potentially confounding variables were considered, but none proved sufficient to explain the genetic relationship. It is concluded that some factor is transmitted by the biological parent that increases the likelihood of the offspring's conviction for criminal offenses. This implies that biological factors are involved in the etiology of at least some criminal behaviors. 6 tables, 1 figure, and 18 references (Author summary modified)