This study evaluated weight change and caregiver stress in 200 informal caregivers to elderly patients discharged from a rehabilitation hospital. Previous laboratory and epidemiologic studies have shown that stress predisposes to weight change. Nineteen percent of the caregivers had gained or lost at least 10 pounds since becoming caregivers. Weight change was significantly associated with higher scores on standardized measures of burden and stress (e.g., Burden Interview, Perceived Stress Scale, Geriatric Depression Scale) and with lower education, poorer self-rated health, more psychotropic medication use, and caring for patients with more ADL limitations who had been hospitalized for stroke or a frail elderly condition. Caregivers to patients with a stroke or frail elderly condition reported 2.8 times more weight change than caregivers to patients with a rehabilitation problem. These results suggest that weight change is a valid indicator of stress in caregivers, and they have public health, clinical, and research applications.