Guided by the affective spillover hypothesis, the present study examined the mediational role of parental adrenocortical reactivity to interparental conflict in explaining associations between interparental conflict and subsequent changes in mothers' and fathers' parenting practices over a 2-year period in a sample of 202 parents and their 6-year-old children. Results of autoregressive path models indicated that marital withdrawal was associated with increases in adrenocortical reactivity to conflict for mothers but not fathers. Furthermore, elevated adrenocortical reactivity in turn predicted greater psychologically controlling parenting practices and inconsistent discipline over time for mothers, but was not associated with changes in maternal warmth. Implications for clinicians and therapists working with maritally distressed parents and families are discussed.