Information on all nonfamilial adoptions in Denmark between 1924 and 1947 (N=14,427) were obtained from records at the Ministry of Justice. Court convictions were used as an index of criminal involvement. Information from the adoption files gave the birthplaces of the biological and adoptive parents; birthplaces for the adoptees were obtained from the Central Persons Register or the local Population Registers. Convictions were determined for adoptees, adopted parents, and biological parents. The biological fathers' and male adoptee conviction rates were considerably higher than the rates for the adoptive father. The male adoptees and the biological fathers were more heavily recidivistic. The rates of conviction for the women were considerably lower, and there was considerably less recidivism. The chronic male adoptee offenders with biological parents having three or more offenses comprised only 1 percent of the male adoptees in the sample, but they were responsible for 30 percent of the male adoptee convictions. The mean number of convictions for the chronic adoptee offenders increased sharply as a function of biological parent recidivism. There was no evidence that type of biological-parent crime was related to type of adoptee crime. A number of potentially confounding variables were considered, but none of these proved sufficient to undermine the apparent genetic influence upon criminal behavior. Methodological issues are discussed, and graphic and tabular data are provided, along with 11 notes and 12 references.