In order to assess the value of Doppler tissue imaging (DTI) in the differentiation of physiological hypertrophy of athletes from primary hypertrophic cardiomyopathy (HCM), the authors compared a group of 20 normal, non-athletic subjects, a group of 43 competitive athletes and a group of 20 patients with mild HCM. In addition to the conventional echocardiographic criteria, the velocity of wall motion at the endocardium and epicardium of the interventricular septum and the posterior wall as well as their gradients, were measured throughout the cardiac cycle. No significant difference was observed between normal subjects and the athletes with respect to velocities and the gradients of velocity. Early diastolic velocities of the posterior wall and interventricular septum were significantly lower than those of normal subjects and athletes. The systolic and early diastolic gradients of velocity of the posterior wall were significantly lower in HCM compared with the normal subjects and athletes. The gradient of velocity between the endocardium and epicardium of the interventricular septum was significantly lower in HCM compared with normal subjects in early diastole and with athletes in systole and early diastole. The best Doppler tissue imaging parameter to differentiate pathological hypertrophy of HCM from physiological hypertrophy of athletes was analysis of the gradient of velocity in early diastole of the posterior wall. A value of 0.7 sec-1 differentiated HCM with a sensitivity of 89%, a specificity of 95% and a diagnostic accuracy of 94%. Doppler tissue imaging is a more sensitive and specific technique than conventional Doppler echocardiography for detecting moderate forms of HCM.