Left ventricular (LV) diastolic function has been causally deteriorated on hypotensive episodes during hemodialysis (ΗD). The influence of intravascular volume deterioration and arterial pressure reduction on LV function in patients without hypotensive episodes during ΗD has not been adequately studied. 23 patients on ΗD were studied for 48±35 months, whose mean age was 50±12 years, their mean body mass index was 24±4kg/m2 and their mean fluid retention between ΗD sessions 2.2±1.1 kgr. We used 2D and Doppler echocardiography before and after the same HD session. The following parameters were measured: a) end-diastolic (LVED) and end-systolic LV diameters, left atrial diameter (LA) and fraction shortening (FS) b) isovolumic relaxation (IVRT) and contraction (ICT) time, deceleration time (DT), Ε and Α waves of the mitral inflow and ejection time (ΕΤ) of the LV outflow velocity. The following indices were calculated: E/A ratio, myocardial performance index (ΜΡΙ) using the (IVRT+ICT)/ET formula, mean arterial pressure (ΜΑΡ), the % reduction in ΜΑΡ and the reduction in intravascular volume after HD. Stroke volume (SV) and corresponding cardiac output (CO), were calculated from the LV outflow velocity waveform. All patients demonstrated systolic arterial pressure at the level of ≥90mmHg and normal FS before ΗD, while they had demonstrated restrictive LV diastolic filling before ΗD. ΜΑΡ, SV, CO, LVΕD, LΑ, Ε wave and Ε/Α decreased while IVRT increased after ΗD (p<0.01). After HD, low ΜΡΙ values (normal range <0.44) were related to greater ultrafiltration volume loss (UFV) (r=0.53, p<0.01) and greater % reduction in ΜΑΡ (r=0.62, p<0.01). Conversely, abnormal ΜΡΙ values were related to high ΜΑΡ after ΗD (r=0,44, p<0.01). Increased UFV was related to greater % increase in IVRT (r=0.43, p<0.01) and % decrease in Ε/Α (r=0.40, p<0.01) after HD. Patients with UFV >3kg (7/23) had lower ΜΡΙ (0.47±0.2 vs. 0.84±0.3, p<0.01) and greater % increase in ΙVRT and % reduction in Ε/Α (p<0.01 ) than those with <3kgr. Fluid retention between ΗD sessions leads to restrictive LV diastolic filling as shown by an Ε/Α>1 and a short IVRT in patients before HD. Reduction in the excess intravascular volume after ΗD normalises ΜΑΡ and thus, improves LV performance.