Animal hoarding is a poorly understood phenomenon, the public health implications of which are not well documented. In this study, professionals dealing with hoarding cases submitted 71 case report forms. The hoarders' residences were characterized by extreme clutter and poor sanitation that impaired ability to maintain functional households. Appliances and utilities were frequently nonfunctional, and animal excrement sometimes accumulated to the extent that the homes were unfit for human habitation. The majority of cases satisfied criteria for adult self-neglect, and dependent elderly people, children, or disabled individuals were present in many of the residences. Animal hoarding may be a sentinel for a range of medical, social, and economic problems. More research addressing the causes and features of animal hoarding is needed to shed light on appropriate interventions.