The objectives of this study were to establish the different developmental trajectories of hyperactive-impulsive behaviors on the basis of both mother and father ratings at 19, 32, 50, and 63 months, and to examine the predictive validity of these trajectories with respect to later hyperactive-impulsive behaviors, as rated by teachers in the first 2 years of school. Hyperactive-impulsive behaviors were assessed in a population-based sample of 1,112 twins (565 boys and 547 girls) at 19, 32, 50, and 63 months of age. The results revealed a differentiated and consistent view of developmental trajectories of hyperactive-impulsive behaviors derived from these repeated assessments, with 7.1% of children seen by mothers (7% for fathers) as displaying high and stable hyperactive-impulsive behaviors. According to mother ratings, children on a high-chronic trajectory were more likely than other children to display hyperactive-impulsive behaviors at 72 and 84 months according to their teachers. Repeated measures over time and father-based trajectories significantly added to the prediction teacher later ratings of hyperactive-impulsive behaviors. These results support the predictive validity of parental assessment of hyperactive-impulsive behaviors during the preschool years and their use to identify children at risk for further evaluation and possible intervention.