Doppler tissue image (DTI) is a newly developed method for measuring myocardial velocity using pulse wave Doppler (P-DTI), or color Doppler (C-DTI) imaging. The major application of DTI is is quantifying systolic and diastolic heart function. DTI can be applied for the quantification of systolic myocardial velocity (Sm) during myocardial ischemia at rest and with pharmacologic or exercise testing. DTI can also detect myocardial dysfunction earlier than the conventional wall motion score system. It is also used for the discrimination of viable and non-viable myocardium. P-DTI is particularly useful in the detection and identification of left ventricular diastolic dysfunction. In particular, it can differentiate normal and pseudonormal patterns. One advantage of DTI is that it is less dependant to the preloading condition of the heart than the conventional method. Recently, DTI has also been applied in the early detection of graft rejection in a transplanted heart. This review summarizes the principles and clinical applications of DTI in the evaluation of left myocardial function.