Fatigue behavior of polyproyleDes filled with three different percentages of CaCO3 (0%, 20%, and 40%) was investigated in this study. Specimens were produced by injection molding. Tensile properties were also evaluated. Tensile-tensile cyclic loading was applied using MTS 810 test apparatus at different frequencies of 23 and 50 Hz. Effects of cyclic frequency and filler content were examined to their fatigue behavior. S-N diagrams were obtained also with normalization of stress amplitudes with respect to their tensile strengths. Besides that temperature rise curves were presented. It is reported that filler content influences the fatigue performance. Increasing the filler content reduces the fatigue performance of PP from pure to PP40, respectively, if normalization effects are not included. The situation differs if normalization effects are included. Results show that fatigue failure mode occurs with thermal fatigue failure mechanism at both frequencies with necking of specimens and it is excessive at higher frequencies and amplitudes. (c) 2005 Elsevier Ltd. All rights reserved.