Fatigue properties of poly(aliphatic/aromatic-ester) (PED) multiblock copolymers were evaluated based on the hysteresis measurement method. This method allows the digitalization of the hysteresis loop and beside the determination of stress and strain-related parameters, stored energy, lost energy, damping and dynamic creep behaviour can be determined. The correlation between hard/soft segment concentration of PED copolymers, and fundamental parameters, which derived during the cyclic loading (using stepwise increasing load testing, SILT), has indicated a good load-carrying performance of polymers containing a high amount of the hard phase. PED copolymers compare very well with commercially available poly(ester-ethers) and show a much better performance than poly(ester-urethanes) when samples are loaded at the same fatigue stress level relative to their ultimate tensile strength. Softer PEDs and poly(ether-urethane) copolymer show much higher values of dynamic modulus than chemically cross-linked silicone elastomer. Therefore, these multiblock copolymers can be considered as good candidates for applications where materials are subjected to oscillatory deformations (for example passive flexor tendon reconstruction). (C) 2003 Elsevier Science Ltd. All rights reserved.