The clinical diagnosis of aortic stenosis (AS) is made by the presence of pulsus parvus et tardus that is the slow rising sustained pulse, heaving apical impulse due to left ventricular hypertrophy and the presence of systolic murmur with or without thrill in the aortic area, right second intercostal space. The murmur is conducted into the carotids; sometimes the high frequency component may be conducted to the apex and may be mistaken for mitral regurgitation. A complete assessment of AS can be made by echocardiography from which diagnostic, prognostic, therapeutic and surgical decisions can be made. This chapter covers the assessment of aortic stenosis, quantitative Doppler echocardiography, other indices of severity of aortic stenosis, correlation of peak gradient, mean gradient and effective orifice area, other echocardiographic modalities, and special considerations in aortic stenosis.