Among a total of 4,862 admittances to a Swedish geriatric hospital and its associated nursing homes, 827 accidents occurred in 588 patients during one year. The purpose of the present study was to establish the direct causes of these accidents and to identify possible risk factors. Information was collected from medical records, interviews with patients and staff, examination of the mental and physical state of the patients, and through reconstruction of the accidents. The investigation embraced 270 patients with 308 major accidents (fractures, sprains, open wounds, concussions and injuries to ligaments), and 318 patients with 519 minor accidents (bruises, contusions, abrasions and minor burns). Injury-free patients with nearest lower bed number in relation to patients with major accidents formed a control group. Patients with previous injuries, balance disturbances, and polypharmacy were at high risk, and intrinsic factors such as dizziness and impaired balance proved to be more significant as direct causes for the occurrence of accidents than environmental factors. The estimated risk for a patient with all these risk factors to have an accident during one year was 94%.