Linear low-density polyethylene (LLDPE), based on butene-1 or hexene-1, was irradiated with gamma-rays under vacuum or in the presence of air. The study focused on the influence of the dose rate and the gamma-dose on the thermal properties of LLDPE. Differential scanning calorimetry, thermogravimetric analysis (TGA), and TGA/FTIR techniques were used to address the thermal behavior as a result of gamma-irradiation. During this irradiation, competition between crosslinking and scission reactions, Subsequent to oxidation reactions, occurred in the polymeric material, which strongly depends on the experimental conditions. A decrease of the crystallinity for gamma-irradiated samples was observed in particular for samples irradiated under vacuum. This observation may be explained by increased hindrance of segment mobility due to crosslinking reactions that prevent crystal growth. TGA investigations revealed an enhancement of the thermal stability for samples irradiated under vacuum but not for those irradiated in air. (c) 2006 Wiley Periodicals, Inc.