OBJECTIVE: The cardiac complications of adenotonsillar hypertrophy (ATH) have been investigated by many scientists by using supplemental diagnostic modalities such as echocardiography. But, arrhythmia analysis has not been studied adequately in patients with ATH. This study aimed at evaluating the prevalence of arrhythmias, heart rate variability (HRV) and heart rate turbulence (HRT) analyses by means of 24 h Holter ECG monitoring in pre- and post-operative periods in children with ATH. METHODS: Twenty-five children with ATH consisting of 12 female and 13 male patients (mean age 66+/-15 months, range 24-108 months) included in this study. All children were assessed pre-operatively and at 1 month post-operatively with 24-h Holter monitoring and ECG analysis. The prevalence analysis of arrhythmias, heart rate variability and heart rate turbulence analysis was assessed. These data were compared. RESULTS: Although some ECG and holter findings such as sinusal tachycardia, Mobitz type 1 second-degree AV block improved after the operation, the prevalence of arrhythmias, HRV and HRT values were not changed significantly in post-operative period (p>0.05). CONCLUSION: Measurement of HRT and HRV are attractive and easily applicable ways of non-invasive risk prediction of cardiac complications. But, these parameters have not changed significantly in post-operative period. However, ECG and 24-h Holter monitoring of electrocardiography may be useful at evaluating the prevalence of arrhythmias and determining cardiac complications in pre-operative period.