The aim of this study was to examine the normative developmental trajectories of aggressive and delinquent behavior in young children. Cohort-sequential univariate latent growth modeling (LGM) analyses were employed to conceptualize and analyze intraindividual changes in children's aggressive and delinquent behavior and interindividual differences in these changes. A multivariate model was tested that related the two developmental trajectories to each other and to harsh discipline. The longitudinal data included mother and father ratings on the Child Behavior Checklist (CBCL) (Achenbach, 1991), the "Leuvens Instrument voor Coercief Opvoedingsgedrag" (Leuvens Instrument of Coercive Parenting Behavior, LICO) (Hellinckx et al., 2000) and the Parenting Scale (Arnold, O'Leary, Wolff, & Acker, 1993) of 674 school-aged boys and girls of a proportional stratified general population sample, assessed annually for three years. A significant nonlinear decline in aggressive and a significant linear decline in delinquent problem behavior were found both in the mother and in the father ratings. A multivariate latent growth analysis indicated that trajectories in aggressive and delinquent problem behavior were positively associated. The association was stronger for boys than for girls. Parenting behaviors were differentially related to children's aggressive and delinquent problem behavior. Coercion was significantly related to aggressive behavior but not to delinquent behavior. Higher scores on coercion were related to higher initial levels and a slower decrease of aggressive behavior. High scores on overreactivity were associated with higher initial levels of aggressive and delinquent problem behavior but not with the growth rates. Boys were higher than girls in initial status. Conversely, the rate of change was not related to gender. The results were replicated in the father reports. (Contains 2 figures and 6 tables.)