The relationship between intelligence, measured regularly from the ages of 3 to 17 years, and registered criminality was investigated for boys (N = 122) in a birth-to-maturity study. Significant negative correlations appeared at several ages, even for intelligence assessed as early as at the age of 3. The hypothesis was advanced that the early language development of the boys would be negatively associated with future criminality. Information on language development, obtained by applying the Brunet-Lézine psychomotor developmental test for infants, substantiated this hypothesis. Significant correlations with registered criminality appeared for language development at 6, 18, and 24 months. Further support for the hypothesized link was provided by psychologists' ratings of children's verbal behavior and by maternal reports of their child's speech at the ages 3 to 5. The role of early language retardation in contributing to later criminality is discussed.