The scaling properties of the fracture surfaces of polyamide 6 are explored in this work. Fracture surfaces were generated by three-point bending on samples with different thermal history and hence different spherulite size distribution. The topometric analysis was based on atomic force microscopy and the self-affine parameters were determined by the variable bandwidth method. Values of the roughness exponent are in the range of 0.84-0.87, which is significantly higher than the so-called universal value of 0.78-0.80 reported for a variety of materials broken in similar kinetic conditions. (C) 2004 Elsevier Ltd. All rights reserved.