Despite increasing interest in the effects of parenting stress on children and families, many questions remain regarding the nature of parenting stress and the mechanism through which stress exerts its influence across time. In this study, cumulative parenting stress was assessed across the preschool period in a sample of 125 typically developing children and their mothers. Indices of parenting stress included both major life events stress-assessed annually from age 3 to 5, and parenting daily hassles assessed every 6 months across the same period. Naturalistic home observations were conducted when children were age 5, during which measures of parent and child interactive behaviour as well as dyadic pleasure and dyadic conflict were obtained. Mothers also completed the CBCL to assess children's behaviour problems. Results indicated that parenting daily hassles and major life stress are relatively stable across the preschool period. Both cumulative stress indices also proved to be important predictors of parent and child behaviour and dyadic interaction, although the predictions were somewhat differential. Despite meaningful relations between the stress factors and child well being, no evidence was found to support the premise that parent behaviour mediates the association between parenting stress and child outcomes. Results are discussed within a developmental framework to understand the stability and complexity of cumulative stress associations to early parent-child relationships. (Contains 6 tables.)