BACKGROUND AND OBJECTIVES: The assessment of left ventricular (LV) diastolic function is important in chronic renal failure because abnormal LV diastolic function has been frequently described in patients on maintenance hemodialysis both during the dialysis and in the dialysis-free interval despite the normal LV systolic function. But the echocardiographic indexes of LV diastolic function is known to be affected by several factors such as loading condition, LV compliance and heart rate. The purpose of this study is to investigate the effect of hemodialysis on the echocardiographic indexes of left ventricular diastolic function in chronic renal failure. Materials AND METHODS: We examined transmitral flow velocity, pulmonary venous flow velocity, and mitral annulus velocity in 20 patients (15 men and 5 women, average 50+/-14, range 19-69 years) of chronic renal failure with normal LV systolic function by echocardiography before and after hemodialysis. RESULTS: 1)According to the body weight change (from 59.5+/-8.3 to 57.2+/-8.1 kg, p=0.0001), after hemodialysis, inferior vena cava dimension (from 18+/-4 to 13+/-5 cm, p=0.0001), left ventricular end-diastolic dimension (from 57+/-6 to 53+/-7 cm, p=0.0001), and left ventricular outflow tract (LVOT)-time velocity integral (TVI, from 26+/-5 to 23+/-5 cm, p=0.004), which reflect intravascular blood volume, decreased significantly. 2)The peak velocity of early transmitral flow (E, from 0.79+/-0.14 to 0.64+/-0.11 m/s, p=0.0001), the peak velocity of late transmitral flow (A, from 0.84+/-0.21 to 0.78+/-0.21 m/s, p=0.011), and E/A ratio (from 0.99+/-0.25 to 0.87+/-0.27, p=0.007) decreased significantly, and deceleration time (DT, from 241+/-48 to 267+/-59 ms, p=0.055) showed tendency of prolongation after hemodialysis. 3)Peak systolic velocity of pulmonary venous flow decreased significantly after hemodialysis (from 0.65+/-0.11 to 0.59+/-0.12 m/s, p=0.042). 4)The difference between duration of reversal flow of pulmonary vein and duration of transmitral flow during atrial contraction (ADD) did not change significantly after hemodialysis (from 5+/-31 to 1+/-29 ms, p=0.502), and did not correlate with the change of peak velocity of early transmitral flow during hemodialysis (DMVE, r=0.390, p=0.089). 5)The peak early diastolic velocity (Ean, from 0.07+/-0.02 to 0.06+/-0.02 m/s, p=0.002) and Ean/the peak late diastolic velocity (Aan) ratio (from 0.78+/-0.27 to 0.62+/-0.19, p=0.003) of medial annulus of mitral valve decreased significantly after hemodialysis. CONCLUSION: Hemodialysis, which reduces LV preload by fluid removal, changes the echocardiographic indexes of left ventricular diastolic function in chronic renal failure. Preload condition need to be accounted for when we evaluate the LV diastolic function with echocardiography.