OBJECTIVE: To study precipitating factors for falls among older people living in residential care facilities. DESIGN: Prospective cohort study. SETTING: Five residential care facilities. PARTICIPANTS: 140 women and 59 men, mean age +/- SD 82.4 +/- 6.8 (range, 65-97). MEASUREMENTS: After baseline assessments, falls in the population were tracked for 1 year. A physician, a nurse, and a physiotherapist investigated each event, and reached a consensus concerning the most probable precipitating factors for the fall. RESULTS: Previous falls and treatment with antidepressants were found to be the most important predisposing factors for falls. Probable precipitating factors could be determined in 331 (68.7%) of the 482 registered falls. Acute disease or symptoms of disease were judged to be precipitating, alone or in combination in 186 (38.6%) of all falls; delirium was a factor in 48 falls (10.0%), and infection, most often urinary tract infection, was a factor in 38 falls (7.9%). Benzodiazepines or neuroleptics were involved in the majority of the 37 falls (7.7%) precipitated by drugs. External factors, such as material defects and obstacles, precipitated 38 (7.9%) of the falls. Other conditions both related to the individual and the environment, such as misinterpretation (eg, overestimation of capacity or forgetfulness), misuse of a roller walker, or mistakes made by the staff were precipitating factors in 83 (17.2%) of falls. CONCLUSION: Among older people in residential care facilities, acute diseases and side effects of drugs are important precipitating factors for falls. Falls should therefore be regarded as a possible symptom of disease or a drug side effect until proven otherwise. Timely correction of precipitating and predisposing factors will help prevent further falls.