KORAF (KORean Atrial Fibrillation) is the prospective study registered electrocardiographically confirmed AF patients who firstly diagnosed at each institute since 2006 and followed up for at least 1 year. Methods: This study is to perform nondirected follow-up to evaluate the clinical course and outcomes of AF. Overall 3,813 patients were enrolled at 27 hospitals in 13 cities of South Korea. A set of standardized data forms were used to obtain clinical information. Follow-up investigations were performed at 1 year. Results: Clinical type of AF was paroxysmal in 43%, firstly detected in 24%, permanent in 14%, and persistent in 12%. 5 major risk factors of AF were hypertension (38.5%), sleep disorders (16.2%), smoking (14.4%), diabetes (13.7%), and congestive heart failure (CHF, 12%). 3 major precipitating factors were mental or psychic stress (14%), alcohol (6%), and sleep apnea (3%). Alcoholic drinking in patients with AF was significantly associated with new onset of AF in ages < 50 years. Older age (>75 yrs, 24%), valvular diseases (17%), diabetes mellitus (12%), history of cerebral thromboembolism (TE, 11%), CHF (8%), and myocardial infarction (5%), who were at particular risk for TE, were fewer than those with low risk, therefore, warfarin was underused (881, 37.5%) and aspirin was more commonly prescribed (1,470, 62.5%). The rhythms at 1-year follow-up were AF in 51% (n=413), normal sinus rhythm in 43% (n=343), and atrial flutter in 2% (n=13). Transient ischemic attack or ischemic TE was developed in 0.7% (n=20). 1.7% (n=46) were died during follow-up. Warfarin did not change 1-year mortality, but aspirin improved survival in this population (OR 0.398, p<0.05). Conclusion: Alcoholic drinking was significantly associated with new onset of AF in younger patients (< 50 years). In this population including relatively younger and paroxysmal AF group, warfarin was underutilized, instead a high percentage were prescribed aspirin, which significantly improved survival.