A new and very convenient route to oxidized poly(ethylene glycol), with a catalytic nitroxyl radical oxidant (2,2,6,6-tetramethyl-1-piperidinyl-oxyl) regenerated in situ by stoichiometric amounts of [bis(acetoxy)-iodo]benzene, is described. Under these conditions, the reaction is quantitative and leads to the pure product by a simple process such as precipitation and washing with diethyl ether.