Objective and methods: The acute changes of circulating oxidative stress parameters were compared in 16 patients undergoing two different apheresis techniques: plasma lipidfiltration (LF) or whole blood dextran sulfate adsorption (DSA). Results: Immediately after apheresis LF was associated with an increase in systemic phagocyte count, enhanced formation of reactive oxygen species and decreased activity of the antioxidant enzyme paraoxonase. After DSA, circulating phagocyte oxidant generating activity was significantly lower. Compared to LF, the systemic level of oxidized LDL and antioxLDL antibodies showed a larger decrease in DSA. All measured oxidative stress parameters returned to nearly pre-apheresis level at day three after apheresis,. Conclusion: The data show a more pronounced leukocyte activation immediately after LF in contrast to DSA, possibly as a consequence of necessity of prior separation of blood plasma. The pathophysiological importance of the short-term oxidative burden after a single apheresis session remains to be determined.