Plasma levels of granulocyte lactoferrin, granulocyte myeloperoxidase and granulocyte elastase in complex with α1-proteinase inhibitor (E-α1PI) were investigated in regular hemodialysis patients dialyzed with hollow-fiber dialyzers made from polycarbonate (FD 100) or cuprophan (GFS 120 H). Plasma levels of all these main granulocyte components increased significantly during hemodialysis. E-α1PI levels were significantly higher in patients dialyzed with the polycarbonate compared with the cuprophan membrane, whereas the increases of myeloperoxidase and lactoferrin were not different for the two dialyzers. On the other hand, plasma C3a levels were higher in patients dialyzed with the cuprophan compared with the polycarbonate dialyzer. Therefore, granulocyte activation during hemodialysis does not necessarily need complement activation.