Purpose: Caregiving research has typically relied on cross-sectional data that focus on the primary caregiver. This approach neglects the dynamic and systemic character of caregiver networks. Our analyses addressed changes in adult child care networks over a 2-year period. Design and Methods: The study relied on pooled data from Waves 1 through 5 of the Health and Retirement Study. Based on a matrix of specific adult child caregivers across two consecutive time points, we assessed changes in any adult child caregiver as well as in the primary adult child caregiver. Results: More than half of all adult-child care networks, including more than one fourth of primary adult child caregivers, changed between waves. Gender composition of the caregiver network and availability of other adult child caregivers were particularly important for network change, but socioeconomic context, caregiver abilities and resources, and caregiver burden played a role as well. Implications: The results underline the need to shift caregiving research toward a dynamic life course and family systems perspective. They also raise concerns about the viability of informal care networks for future smaller birth cohorts and suggest that health care providers need to recognize and address coordination and potential conflicts among care network members. (Contains 5 tables and 1 figure.)