Pulmonary arterial hypertension (PAH) is severe and frequently progressive disease. Therefore, early diagnosis and appropriate management of PAH are essential for good prognosis. As indicated in the evidence-based clinical practice guidelines for PAH, Doppler echocardiography(UCG) is the 'test of the first choice' for noninvasive measurement of pulmonary arterial pressure in patients in whom PAH is clinically suspected. Similarly, comprehensive UCG is valuable in assessing the causes of pulmonary hypertension, such as left ventricular systolic or diastolic dysfunction, valvular heart disease, or intracardiac shunts. In addition, the results of several studies suggest that echocardiographic evaluation of right ventricular structure and function(e.g.Tei index) can provide important prognostic information.