To investigate the influence of moisture and EPR-g-MA content on the fracture behavior of glassfiber reinforced PA6 materials, brittle-to-tough transition temperatures (Tbtt) were determined. Water absorption was taken into account by conditioning the analyzed materials. Tensile tests could reveal the temperature range of the largest moisture dependence of mechanical properties between 10 and 50 degrees C. J-integral values were used to describe the fracture behavior under conditions of impact load as a function of temperature. The brittle-to-tough transition of reinforced polyamides was found to be less approximate than in unreinforced materials. Two different characteristic temperature points Ts and Te were identified, which were the intercept between elastic and elasticplastic deformation on the one hand and the starting point of dominating stable crack propagation with strong plastic deformation on the other hand. Characteristic brittle-to-tough transition temperatures Tbtt could be calculated as the arithmetic average of these two points. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012