Because 7.5-10mEq/l of acetate is indispensable for BCHD fluid, the loading of acetate during BCHD is inevitable. In AFBF, neither dialysis fluid nor substitution fluid contain acetate at all. From acetate toxicity aspect, we are interested in such a little difference. Plasma acetate levels and circuratory stabilities in BCHD Were compared with those in AFBF among the 10 clinically stable patients on chronic BCHD. In both 18 sessions, dialyzers, QB, QD, and body weight changes were maintained unchanged. Plasma acetate increased significantly from 0.62 to 1.06mEq/l (p<0.01) in BCHD, while it did not change from 0.56 to 0.55mEq/l in AFBF.7 hypotension episodes needed total 1350ml of saline infusion and 890ml of hypertonic glycerol solution (HGS) in BCHD. While, 5 episodes needed 550ml saline and 490ml HGS in AFBF. But unfortunately, we could not find the significant difference in hypotension episodes appearance lates in the present study. In conclusions, AFBF could possibly decrease the hypotension episodes, depending on the tiny differences of plasma acetate levels. Further study should be requested in this field.