Background:Congenital hypothyroidism is one of the most common preventable causes of mental retardation. In most cases, the disorder is permanent and results from an abnormality in thyroid gland development. Less commonly, the altered neonatal thyroid function is transient, attributable to the transplacental passage of maternal medication, maternal blocking antibodies, or iodine deficiency or excess.The objectives of this study were to evaluate ventricular function changes in patients with congenital hypothyroidism. Methods:This was a case- control study that was carried out at pediatric cardiology and endocrinology units of Zagazig University Children’s hospital on 74 children with hypothyroidism and control subjects using conventional Echocardiography, pulsed wave tissue Doppler and auto-strain of right ventricle. Serum free thyroxine (T4) and thyroid-stimulating hormone (TSH) levels were measured in case and control groups. Results:There wereno statistically significant differencesbetween cases and control groupregarding early diastolic wave, late diastolic wave, and systolic wave velocities[11.6 (8.04-13.88), 6.66 (5.77-8.65), 6.85±1.06 vs 13.1 (8.68-14.7), 7.16 (6.36-9.08), 6.64±1.36, P> 0.05]. Left ventricular tissue Doppler-derived MPI was higher in our cases compared with control group[0.8 (0.68-1.08) vs 0.53 (0.45-0.72), p< 0.001]. There was significant positive correlation between serum T4 level and É wave velocity of RV (r=0.337, p=0.019).Conclusion:Left ventricular tissue Doppler-derived MPI was higher in our cases compared with control group which denotes LV subclinical systolic and diastolic dysfunction in patients with congenital hypothyroidism although LV EF and FS were normal in these patients. Subtle right ventricularsystolic and diastolic impairment is present in patients with congenital hypothyroidism.Global RV strain was less in our patients compared with control group indicating impairment of RV systolic function.Serum T4 has an important rolein maintenance of RV early diastolic velocity