Background/Aims: Assessing the volume status of hemodialysis (HD) patients and determining their adequate dry weight (DW) present great challenges for physicians involved in HD. In this study the relationship between standardized filtration coefficients of microvasculature (Lpst) and the plasma atrial natriuretic peptide (ANP) levels or echocardiographic measurements (UCGm) were clarified. The aim of this study was to evaluate the possibility of utilizing Lpst as one of the tools for assessing volume status of patients undergoing HD. Methods: 52 patients on maintenance HD were examined. Lpst was calculated by utilizing continuous measurements of blood volume during HD by means of monitoring changes of hematocrit with CRIT-LINE<sup>TM</sup>. Plasma ANP levels were measured shortly after HD. Plasma ANP levels were elevated beyond the normal limit in 32 patients (Hi group) and were within the normal range in the remaining 20 patients (Lo group). UCGm were performed within 1 month prior to the study. Inferior vena cava diameters in quiet expiration (IVCe) were dilated in 21 patients (Hivc group) and were within the normal range in the remaining 31 patients (Livc group). Lpst was compared with plasma ANP level and UCGm. Results: Lpst in Lo group were significantly lower than those in the Hi group (0.83 ± 0.19 vs. 2.64 ± 2.73 ml/mm Hg/min; p < 0.001). Lpst correlated significantly with plasma ANP levels (r = 0.613; p < 0.001). Lpst in the Livc group were significantly lower than those in the Hivc group (1.33± 1.61 vs. 2.85 ± 2.88 ml/mm Hg/min; p < 0.001). Lpst also correlated with IVCe (r = 0.630; p < 0.001). The receiver operating characteristic (ROC) curves for high plasma ANP level and for dilated IVCe were significant for Lpst. Area under the ROC curve for elevated ANP was 0.909 (95% confidence interval (CI) 0.834–0.985) and for dilated IVCe was 0.833 (95% CI 0.724–0.941). Conclusion: We conclude that there exists a significant association between Lpst and plasma ANP levels at the end of a dialysis session. There is a possibility that high plasma ANP levels cause elevation of Lpst. Besides ANP, Lpst significantly correlated with IVCe. These results suggested that Lpst can be utilized as one of the tools for assessing volume status of patients undergoing HD.