Objective: Pronounced pulmonary circulation overloading has been observed in hemodialysis patients with higher fluid intake over the long interdialytic interval. This study aimed to evaluate the impact of the degree of fluid accumulation on left ventricular (LV) systolic and diastolic function and sizing characteristics. Design and method: For the present analysis, 41 patients receiving maintenance hemodialysis thrice-weekly were divided by the recommended threshold of interdialytic-weight- gain corrected for dry weight (IDWG%) into a higher (>4.5%) and a lower ( < 4.5%) IDWG% group. All participants underwent 4 echocardiographic assessments at the start and the end of the 3-day and the 2-day interdialytic interval in a crossover design. Results: Over the 3-day interval, significant increments in stroke volume (SV) were observed for both groups, but were more prominent in the higher IDWG% group (>4.5% 18.63 ± 22.84vs. <4.5%12.6 ± 14.48mmHg, p = 0.04). Similarly, a greater increase in cardiac output was evidenced in patients with higher IDWG% over the 2- day interval (>4.5%1.31 ± 1.38 vs.<4.5%0.36 ± 2.08L/m 2, p = 0.012). With regards to diastolic function, a significant increase in E/A and E/E’m ratios was observed over the 3-day interval, but significant between-group differences in interdialytic changes were detected only for the E/A ratio (IDWG>4.5% 0.35 ± 0.29 vs. <4.5% 0.06 ± 0.44, p = 0.035). Left atrial dimensions and LV mass were enlarged to a similar extent in both study-groups during both intervals. Conclusions: Patients exceeding the recommended threshold of interdialytic fluid accumulation experience higher increases in SV and deterioration of preload- dependent indexes of diastolic function, particularly during the 3-day interval.