The effects of gamma irradiation on polymers used in food packaging have been studied by NMR. In order to assess the presence of a threshold dose for an observable effect, the whole range of 1-100 kGy was investigated. Polystyrene, poly-butadiene, styrene-acrylonitrile. high-impact polystyrene and acrylonitrile-butadiene-styrene were studied before and after the gamma irradiation treatment and in the presence or in the absence of antioxidants and stabilizers. In the absence of stabilizers, the effect of gamma irradiation on polystyrene is negligible even when operating at high doses. In contrast, the role of antioxidants and stabilizers is crucial in poly-butadiene and butadiene-containing copolymers. High-resolution NMR, dynamic mechanical analysis, impact analysis and gel permeation chromatography performed on irradiated polystyrene samples do not show any detectable effect, confirming polystyrene as an ideal polymer for food packaging use. (C) 2000 Elsevier Science Ltd. All rights reserved.