Objective: Cardiac complications are the major cause of morbidity and mortality in beta-thalassemia major. The aim of the study was to evaluate right (RV) and left (LV) ventricular systolic and diastolic functions using myocardial performance index in young, asymptomatic children suffering from thalassemia major, for early detection of cardiac function impairment, preventing further cardiac damage by modifying disease progression and treatment. Methods: A case-controlled, cross-sectional study involving 80 patients suffering from beta- thalassemia major and 80 children adjusted in terms of age and sex served as a control group were studied in Research Center for Children and Adolescent Health Zahedan. The relevant echocardiographic parameters were measured in both subject groups: myocardial performance index (MPI), isovolumic relaxation time (IRT), isovolumic contraction time (ICT), pre-ejection period (PEP), ejection time (ET), PEP/ET ratio, deceleration time (DT) and acceleration time (AT). Data were analyzed by unpaired Student t test. Results: The left ventricular mean IRT in the patient group was 114±21 and in the control group 94±10 msec (p<0.05). The mean MPI (LV) in the patient group was 0.58±0.18 and in the control group 0.41±0.08 (p<0.05). The mean ET (LV) in the patient group was 237±36 msec and in the control group 266±25 msec (p<0.05). The mean ET (RV) in the patient group was 237±39 msec and in the control group 261±36 msec (p<0.05). Conclusion: There is an early systolic and diastolic dysfunction in children younger than 10 years with beta-thalassemia major. Even in young asymptomatic children with beta-thalassemia major, serial echocardiography seems warranted in order to adjust cardioprotective therapy.