Using a daily diary design, we examined fluctuations in caregiver well-being; how day-to-day variations in stressors related to the caregiving experience are linked to fluctuations in well-being; and whether caregivers who are women, or high on certain personality traits (e.g., neuroticism) are more susceptible to emotional/physical health fluctuations in the face of daily stressors. Sixty-three caregivers reported on eight consecutive days. Multilevel analyses (Hierarchical Linear Modeling) indicated significant within-person reactivity. On days when caregivers faced more tasks than usual, more care recipient behavior problems, or more family disagreements regarding care, they experienced more depressive symptoms, feelings of burden, and physical symptoms. Some within-person patterns of reactivity were moderated by gender and personality. Implications for community interventions for caregivers are discussed.