Background: Atrial fibrillation (AF) is the most common arrhythmia. It is associated with significant morbidity and mortality. The size and volume of left atrium is an important development of atrial fibrillation which land up subjects into various complications so present study was carried out to study echocardiography findings (size and volume) among AF Cases with various underlying aetiology. Material and methods: A cross–sectional observational study was conducted for duration of 2 years to measure left atrial size and volume by echocardiography in patients of atrial fibrillation in various diseases. A proforma was designed to collect the desired information from the patients. The preformed structured proforma consisted of recording of investigations was used as data collection tool. All efforts were made to diagnose the aetiology of atrial fibrillation. Results: A total of 50 cases of AF were studied with mean age of study participants 53.68±12.74 yrs (range 25–80yrs) and F: M–1.3:1. Major risk factors found were RHD (44%) Hypertension (28%) IHD (24%) and DM (14%).Mean LA volume and size on echo measurement was 78.16ml and 28.88cm2.There was significant dilatation of LA among RHD with p<0.05 among major risk factors found in study