An investigation of the influence of different types of carbon black on fatigue crack-growth behavior was undertaken. Fatigue tests were carried out on edge-notched specimens under cyclic tension loading. A power-law dependency between the crack-growth rate and tearing energy was obtained. Natural rubber (NR) filled with N330 (the mean diameter is 30 nm) carbon black possessed the lowest values of exponent b and constant B (the two crack growth parameters determined from cyclic crack growth testing), which denoted the strongest resistance to crack growth at a given tearing energy. Strain-induced crystallization was investigated by the modified Mooney-Rivlin equation and showed the earliest appearance and strongest ability of the crystallization of the NR/N330 composite at the largest amount of bound rubber. The study on the viscoelastic properties by dynamic mechanical analysis confirmed that the NR/N330 composite had the largest viscoelastic contribution, which was attributed to the viscoelastic dissipation in the viscoelastic region in front of the crack tip. All of these results confirm the best crack-propagation resistance of NR filled with N330. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 3441-3447, 2010