The reaction of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) with I-butyl hydroperoxide, in the presence of catalytic amounts of Fem yields oxygen. This reaction, which has never been described in the literature so far, led us to envisage a totally new concept, involving the reaction of TEMPO with oxygen-centered radicals. The formation of an intermediate has been detected during the course of the reaction. A mechanism based on the experimental facts and literature data is proposed. (C) 1998 Elsevier Science Ltd. All rights reserved.