Background/Aims: Filtration coefficients (Lp) and plasma volume were estimated in order to investigate whether suppressed Lp associates with intradialytic hypotension and/or diabetic nephropathy. Methods: Twenty-one patients were evaluated. Nine patients were diabetic (DM) and 12 were nondiabetic (non-DM). Three of DM and 4 of non-DM were prone to dialysis-induced hypotension (hypo(+)) and others (hypo(–)) were not. Changes in hematocrit (Ht) were measured for 60 min after the start of ultrafiltration. Lp and plasma volume at the start of ultrafiltration (Vp0) were estimated to fit calculating values of Ht based on Schneditz’s open two compartment model to actual value. Results: There was no significant difference in the mean values of Lp/Vp0 either between hypo(+) and hypo(–) (0.87 ± 0.37 vs. 1.24 ± 0.48 ml/mm Hg·min·liter; n.s.) or between DM and non-DM (1.04 ± 0.32 vs. 1.17 ± 0.56 ml/mm Hg·min· liter; n.s.). However, the comparisons of Lp/Vp0 among the four groups (hypo(+)/DM, hypo(–)/DM, hypo(+)/non-DM and hypo(–)/non-DM) showed significant differences between hypo(+)/non-DM and hypo(–)/non-DM (1.08 ± 0.40, 1.02 ± 0.32, 0.71 ± 0.29*, 1.40 ± 0.53* ml/mm Hg·min·liter; *p < 0.05). Differences in the percentage of Vp0 to body weight (Vp0/BW) among four groups and correlation between Lp/Vp0 and Vp0/BW were not significant. Conclusion: These data indicated that reduction of Lp/Vp0 was not simply caused by decreased circulating plasma volume (Vp0/BW) and that the suppressed filtration coefficients may have substantial association with dialysis-induced hypotension in non-DM. The estimation of Lp using in-line measurement of Ht was a useful method for analyzing intradialytic hypotension.