Atrial fibrillation (AF) is the most common sustained arrhythmia in the World, occurring in approximately 0.4% of the general population. The purpose of the present study was to see the aetiology, presenting symptoms and risk stratification of hospital admitted patients with atrial fibrillation. It was conducted in the department of cardiology, University Cardiac Centre, Bangabandhu Sheikh Mujib Medical University, Dhaka from January 2008 to January 2009. A total of 100 patients with atrial fibrillation were enrolled in this study. Out of them, male were 40(40%) and female 60(60%); age range 22-79 years. Most common presenting symptoms were palpitation (80%) & dyspnoea (70%). Chronic rheumatic heart disease (CRHD) (63%) was found in most cases followed by IHD (13%), hypertension (11%). Among CRHD, mitral stenosis was 50%, and mixed mitral valve disease was 8%. Risk stratification of patients with AF for future thromboembolism revealed high risk factors were present in 60% cases, moderate in 25% cases, and weaker risk factors in 15% cases. According to CHADS2 score, most of the patients belonged to moderate risk group (47%) and 32% in low risk group. Chronic rheumatic heart disease is one of the major causes of atrial fibrillation in hospital admitted patients & risk stratification revealed that most of the patients were in risk for future stroke.