Thromboembolic complications (cerebral infarction and system embolism) are the most threatening ones in patients with ciliary arrhythmia without valvular lesions. Transoesofhageal echocardiography is the method of choice in detection of left atrial auricle thrombosis, which is the main source of thromboembolism in this category of patients. Primary and secondary prevention of thromboembolic complications in patients with ciliary arrhythmia is a topical problem, still remaining unsolved. Administration of indirect anticoagulants, which are the preparations of choice, demands strict doctor's supervision and continuous laboratory monitoring. The study presents authors' own data, based upon the observation of patients treated with either warfarin or acenocumarol. The paper demonstrates equal efficiency of both cumarine anticoagulants. The frequency of haemorrhagic complications after 12-month therapy with either warfarin or acenocumorol in patients with ciliary arrhythmia without valvular lesions was comparable. Warfarin provided more stable level of anticoagulation and thus long-term warfarin therapy was characterized by lower risk of complication.