The development and testing of a multidimensional instrument to assess the reactions of family members caring for elderly persons with physical impairments, Alzheimer's disease, and cancer is reported. Forty items were administered to a sample of 377 caregivers of persons with physical impairments and Alzheimer's disease. Five dimensions of caregivers' reactions were identified through exploratory factor analysis. Using confirmatory factor analysis on an independent sample (N = 377), these dimensions were tested for factorial invariance across spouse and nonspouse caregivers and between caregivers of persons with cancer and those caring for persons with Alzheimer's disease. The subscales also had a high level of factorial invariance across a three-wave panel study (N = 185). The subscales appeared consistent with first order tests of construct validity.