Abstract: An endotoxin binding material affixed to a support is disclosed. One embodiment is a matrix material capable of binding endotoxins and comprising a polar, water-insoluble, high molecular weight polymer support to which is attached groups which adsorb endotoxin molecules. The groups comprise bifunctional aliphatic molecules, one end of which is bound to the support, the other end of which is bound to an aryl molecule. The invention has utility in the removal of endotoxins from biological fluids and other solutions and for concentrating endotoxins so that they may be subsequently detected and quantified.