Diastolic function evaluation should be considered an integral part of a standard echocardiogram. Currently, echocardiography is the best noninvasive method to assess diastolic function and to estimate filling pressures. 2D echocardiography for left atrial size, left ventricular (LV) size and function, pulse and continuous wave Doppler study for mitral inflow and tricuspid regurgitation velocity, and tissue Doppler study for septal and lateral annulus tissue velocities and E/e′ ratio are the main parameters for evaluating the diastolic function. However, the first step before starting LV diastolic function assessment is determining whether LV systolic function is normal or reduced and if the patient has any structural heart disease since they have different diastolic function algorithms and approaches. In this chapter, we will discuss the diastolic filling pattern/pressure, grading diastolic dysfunction in the setting of reduced LV systolic function, and how to assess diastolic function in the special population, which the general algorithm cannot be used.