Injuries due to interaction with dogs and cats are not uncommon, and constituted 1.4% of all injuries in an unselected policlinical and inpatient material. This material was collected from a population of 135,000 people in Northern Sweden, and during 2 years 280 patients with injuries related to these domestic animals were found (Ndogs = 212, Ncats = 68). The injuries were in most cases caused by bites and by falls. The former were more common among men, the latter more common among women and related to fractures and dislocations. In contrast to many previous investigations, bite injuries were more common among adults than among children, possibly related to national differences in the keeping of dogs. Most dog related injuries were caused by the owner's dog. Walking the dog was the activity most often related to personal injury. The cost for inpatient cases (treated at the University Hospital, Umeå) caused by dogs and cats is of the same magnitude as the cost due to motorcycling in traffic, but less than the cost for injuries sustained during horseback riding and other horse related activities, for soccer, snowmobiling and for assaults.