Clarifying processes associated with emerging externalizing behavior problems during early childhood was the focus of this study. Data were collected from 100 parent-child dyads when children were 2, 3, and 4 years. An incremental risk model was hypothesized to explain the emergence of externalizing behavior problems. Theoretically, children's temperamental propensity towards negative emotional reactivity increases risk for noncompliance, noncompliance that increases risk for externalizing behaviors by age 4. Parenting was identified as the mechanism by which children's progression along the incremental risk pathway is amplified or minimized; progression is only expected under conditions of harsh parenting. No statistical support emerged for the incremental risk model or the moderational effects of harsh parenting. Harsh parenting was a statistically significant predictor of children's noncompliance one year later. Implications of the current findings for future research are discussed.