Sterile inflammatory reactions of varying degree are a rare, but not uncommon complication after intraocular lens implantation. At present we still do not know the cause of these processes, but we consider two chemical substances at least as risk factors for them: the lens content of monomeric methyl methacrylate, which is present in any lens made from polymethyl methacrylate (Perspex), and the lens content of ethylene oxide, an extremely toxic agent, which is absorbed by the lens during sterilization with this gas. Gaschromatographic investigations show that under sterilization of intraocular lenses by Co60-radiation the lens content of monomeric methylmethacrylate can be reduced drastically. Also, any contamination of the lens by ethylene oxide is avoided. Therefore at least two important arguments speak in favour of this alternative sterilization technique.