In this study stealing is considered as a form of aggressive behavior and related to the factors of chronological maturity and mental capacity. The cases used were children examined in the Psychiatric Clinic connected with the Department of Public Welfare in St. Louis. A larger proportion of boys than girls were known to steal, and a larger proportion known not to steal. The question of stealing was left undetermined in a larger proportion of girls' cases. Of children known to steal 34% had I.Q.'s below 70, of those who did not steal 47% were below this level, and in the group in which stealing was undetermined 58% were below 70. The chronological ages of the three groups were about the same, but the mental age of children known to steal was 16 months above that of children who did not steal, and 28 months above that of children about whom no stealing was reported. The differences between their chronological ages were not significant, but the differences between their mental ages were significant. (PsycINFO Database Record (c) 2006 APA, all rights reserved)