The development of inattentiveness and hyperactivity in middle childhood was investigated using a prospective longitudinal approach. Endogenous and exogenous predictors measured in infancy and in early and middle childhood were examined independently and in combination. In early childhood, quality of caregiving more powerfully predicted distractibility, an early precursor of hyperactivity, than did early biological or temperament factors. Caregiving and contextual factors together with early distractibility significantly predicted hyperactivity in middle childhood. While environmental variables also predicted hyperactivity in later elementary years, these factors did not improve the prediction beyond the influence of hyperactivity in early elementary years. The findings support a developmental view of the origins and course of hyperactivity in childhood, that is, that the emergence and persistence of AD/HD symptoms depend on developmental history along with current circumstances.