BACKGROUND: In clinical guidelines regarding atrial fibrillation, oral anticoagulation is recommended for patients over the age of 65 or with additional risk factors. The aim of the present study was to investigate how these recommendations are followed in clinical practice. MATERIAL AND METHODS: A retrospective study was conducted among patients hospitalized for atrial fibrillation at Tromsø University Hospital from 1995 to 1998. Data were obtained from hospital files. RESULTS: 362 patients with atrial fibrillation (57% men), mean age 68.4 years (range 24-96), were included. 23.5% had their first atrial fibrillation event. 224 (62%) patients experienced successful cardioversion during hospitalization(s), while 138 (38%) were discharged from hospital with chronic atrial fibrillation. 97 (70%) of these patients were given warfarin at discharge. Previous stroke and atrial fibrillation were significant predictors for warfarin prescription. Prescription did not increase with age. 28 (20%) of patients with chronic atrial fibrillation received acetylsalicylic acid, while 16 (12%) were not given antithrombotic treatment. INTERPRETATION: This study indicates a high degree of implementation of guidelines for antithrombotic treatment of patients with chronic atrial fibrillation in hospital practice.