In a controlled prospective trial, the effect of a switch from cellulose-based, low-flux dialysis membranes to polysulphone, high-flux membranes on lipid parameters was evaluated. Baseline values of lipid parameters were identical in the study group and the control group in which the dialysis membrane remained unchanged. After 6 wk, total triglyceride, very low-density lipoprotein (VLDL) triglyceride, and VLDL cholesterol decreased, respectively, 28 +/- 17 (P < 0.01), 38 +/- 17 (P < 0.01), and 24 +/- 21% (P < 0.05), and the proportion of total cholesterol that was high-density lipoprotein cholesterol increased from 15 +/- 5 to 18 +/- 5% (P < 0.05) in the high-flux polysulphone group, whereas these variables remained unchanged in the control group. Low-density lipoprotein and total cholesterol as well as Kt/V, protein catabolic rate, parathyroid hormone, albumin, and body weight did not change. No change in lipoprotein lipase activity was found. In a second study, the effects of a single hemodialysis session with high-flux polysulphone and low-flux, cellulose-based membranes on lipid parameters and lipolytic activity were compared in a cross-over fashion. Treatment with both membranes resulted in a significant decrease in plasma triglyceride, VLDL triglyceride, and VLDL cholesterol. Lipoprotein lipase activity increased during hemodialysis. Changes in lipid parameters and lipolytic activity were identical during the two treatments.