This study analyzed Early Head Start Research and Evaluation (EHSRE) study data, examining the effect of parenting classes on parenting behaviors and children's cognitive outcomes. The study analyzed three sets of dependent variables: parental language and cognitive stimulation, parent-child interactive activities, and the Bayley Mental Development Index (MDI) of children. The analysis results, using Longitudinal Hierarchical Linear Modeling (HLM) and multivariate analyses, revealed that parents who attended parenting classes stimulated their children's language and cognitive development and provided educational activities more than did parents who did not participate in parenting classes. The cognitive outcomes (the Bayley MDI scores) of the children whose parents attended parenting classes were significantly higher than those of the children of parents who had never attended these classes. (Contains 6 tables and 8 figures.)