Aim of the study was to assess reproducibility and diagnostic value of E100 event recorder for patients with complains on heart arrhythmias and no abnormalities on multiple routine ECGs and/or 24-hour Holter ECG monitoring and the second one, an assessment of adherence and attitude of patients to the E100 event recorder, dependent on the results of self- assessment questionnaires. 24 patients with complains on heart arrhythmias were included in the study. All the patients were provided with the REKA E100 event monitors for 5 ± 2 days and self-assessment questionnaires to assess level of adherence and attitude of patients to the E100 event recorder. E100 event recorders revealed junctional rhythm (n=2), AV nodal reentrant tachycardia (n=2), extrasystolic arrhythmias (n=10), atrial fibrillation (n=2), WPW syndrome (n=4), ventricular tachycardia (n=1), sinus tachycardia (n=7) and complete AV block (n=1). Majority of patients consider device as easy to use, comfortable and safe. In comparison with multiple routine ECGs and 24-hour Holter ECG monitoring, E100 event recorders showed higher reproducibility and efficacy for detecting and interpreting heart arrhythmias.