Many studies have hypothesized a developmental relationship between children's chronological and mental ages and their intrapersonal perceptions of internal and external control. To investigate longitudinal changes in children's locus of control, 97 elementary school children, between the ages of 8 and 13, were administered the Children's Nowicki/Strickland Locus of Control Scale annually for 3 years. An analysis of the results showed that children's mean locus of control scores were significantly different from one age group to the next as well as from one year to the next. Older children had significantly more internal scores than younger children, and the same 97 children, each succeeding year, demonstrated significant increases in internal perceptions. No significant differences between sexes were observed in this generally linear developmental trend. The study supports the hypothesis that increases in internal perceptions are associated with growing older. (Author/BL)