Background: Diabetes Mellitus (DM) is a serious global health problem currently reaching epidemic proportions. It may be complicated with cardiomyopathy. Pulsed wave tissue Doppler can provide quantitative diagnostic information for the assessment of myocardial systolic and diastolic velocity. Objective: Our studyaimed to assess ventricular myocardial performance in type I diabetes mellitus using tissue Doppler echocardiography. Patients and Methods: This study was carried out at Pediatric Cardiology Unit, Zagazig University Hospitals. 64 age- and sex-matched children were classified into case group included 32 type 1 DM and control group included 32 healthy children. They underwent complete history and conventional and tissue Doppler echocardiographic examination. Results: E` wave velocity was lower in cases compared to control children (p <0.001). A positive correlation was found between mitral annular À wave velocity andleft ventricular myocardial performance index (LV MPI) measured by tissue Doppler imaging. Conclusion: Early diastolic dysfunction was found in our patients evidenced by reduced E` wave velocity measured by tissue Doppler imaging. The absolute value of LV MPI was higher in patients compared to control children. A finding designating that statistical significance may be found at a longer term follow up study of our diabetic children. LV tissue Doppler-derived MPI was found to have significant positive correlation with mitral annular À wave velocity although systolic LV function was normal in patients when measured by traditional echocardiography in terms of EF and FS.