We have investigated extrusion moulding for 13 processing cycles, using formulations containing virgin polypropylene and 1:1 mixtures of virgin and post-consumer polypropylene containing, or not, the antioxidant Recyclostab 411(TM). The main effect of reprocessing for polypropylene was the decrease of molar mass due to degradation with chain scission, which was detected by the melt flow rate and the increase in crystallinity. Antioxidant consumption and material stability reduction with processing cycles were observed by the reduction of the thermo-oxidative stability detected by oxidative induction time measurements. The addition of antioxidants minimized degradation and maintained the stability of the material. (C) 2002 Elsevier Science Ltd. All rights reserved.783491495