Family caregiving research is increasingly contextual and dynamic, but few studies have examined prevalence and predictors of change in primary caregivers, those with the most frequent contact with healthcare professionals. We identified prevalence and predictors of 2-year change in primary adult-child caregivers. Data pooled from the 1992-2000 waves of the Health and Retirement Study (HRS) represent 1,068 parent-level care occasions and 3,616 child-level occasions. There is considerable 2-year stability in primary adult-child caregivers. Parents are more prone to experience a change in adult-child primary caregivers if they live by themselves and if they have more sons and daughters. As far as the adult children are concerned, daughters and children living closer to parents are more likely to remain primary caregivers. Results suggest that change in primary caregivers is more strongly associated with available alternatives and gender norms than burden and competing obligations. (Contains 4 tables.)