Patients on hemodialysis for end-stage renal disease frequently have increased levels of lipoproteins and beta-2 microglobulin (B2M). In an effort to assess the effect of hemodiafiltration on TACUrea, delivered Kt/VUrea, normalized protein catabolic rate, and B2M level, 6 chronic hemodialysis patients (mean age 63.3 +/- 17 years; 3 men, 3 women) were randomly selected to undergo 4 weeks of hemodiafiltration. The therapy consisted of Qb: 400 ml/min, Qd: 800 ml/min, time: 3.5 hours and 10 L hemofiltrate exchanges with either Ringer's lactate or combination of Ringer's solution and saline using polysulfone membrane dialyzer. TACUrea, Kt/VUrea delivered, normalized protein catabolic rate, serum electrolytes, liver enzymes, lipoproteins, and B2M clearance were evaluated before and after hemodiafiltration. Kt/V increased significantly [pre: 1.3 +/- 0.2 vs post: 1.8 +/- 0.3; p < 0.05], and TACUrea decreased (pre: 44.3 +/- 15 vs post 32 +/- 6.7 mg/dl; p < 0.1). There was no change in normalized protein catabolic rate (pre: 0.88 +/- 0.21 vs post: 0.80 +/- 0.15). B2M clearance was greatly enhanced (pre: 22 +/- 11 vs post: 110 +/- 36 ml/min; p < 0.001) together with a reduction in serum B2M level (pre: 43.6 +/- 11.4 vs 31.2 +/- 6.4 mg/L; p < 0.05). There was no significant increase in total cholesterol, low density lipoprotein, high density lipoprotein, or triglyceride levels, nor was there a change in electrolyte, CO2, or liver enzyme levels. Blood pressure control was satisfactory throughout hemodiafiltration therapy. Hemodiafiltration using a polysulfone membrane dialyzer raised delivered Kt/VUrea and reduced TACUrea and B2M levels significantly.