THE ARTICLE by Brennan and colleagues1 in this issue of the ARCHIVES describes a well-designed and carefully reported study of the linkages between exposure to maternal smoking during pregnancy and later crime. Using data from a large Scandinavian study of male births, the authors established that males whose mothers smoked during pregnancy had significantly higher rates of crime when studied into their middle 30s. These associations persisted when a range of confounding social, family, and maternal factors were taken into account. Results of the study also suggest that, although exposure to maternal smoking during pregnancy is related to life-course persistent offending, it is not related to adolescent-limited offending.