Research on self-control theory consistently supports its central prediction that low self-control significantly affects crime. The theory includes other predictions, however, that have received far less scrutiny. Among these is the argument that self-control is developed early in childhood and that individual differences emerging then persist over time. The purpose of this study is to provide a rigorous test of the stability thesis. First, we examine the extent of stability and change in self-control for a national sample of U.S. children age 7 to age 15. Second, we consider whether parenting continues to affect self-control during adolescence—a period after the point at which self-control differences should be fixed. The analysis revealed strong absolute and relative stability of self-control for more than 80 percent of the sample, and this stability emerged in large part as early as age 7. Contradicting the theory was a smaller portion of respondents (roughly 16 percent) who experienced substantial absolute and relative changes in self-control even after the age of 10. Moreover, parental socialization continued to affect self-control during adolescence, even after accounting for both prior self-control and exposure to parental socialization.