An attempt to find out the causes of atrial fibrillation was made in this study; although this does not represent total picture of whole population as the number of cases was limited and taken from a particular area for a limited period. Among the causes in our country, rheumatic mitral valvular disease topped the list followed by rheumatic multiple valvular disease IHD, HHD; lone atrial fibrillation came in the aetiology sequentially. This information is valuable in regard to management as rheumatic heart disease, the prime cause of atrial fibrillation in our country.