Persons 65 years and older are the most rapidly growing age group in the United States. As age increases, functional ability deteriorates and the need for help from another person escalates. Caring for elderly persons experiencing functional deterioration is stressful, creating hidden patients among caregivers. This study surveyed randomly selected active family practice patients 40 years and older to determine the prevalence and extent of the caregiving role and functional disability among elderly relatives. One in five patients (126/602) surveyed had caregiving responsibilities for noninstitutionalized relatives (total, 153 patients). One third of caregivers lived with the relative; most of the remaining two thirds visited their relative at least twice weekly. Caregivers reported some functional impairment in 60% of their relatives, and substantial impairment in 40%. The caregiving experience is common, and the potential for stress from managing an elderly relative's disability is substantial. Further research is needed to elaborate on the burden of the caregiver.