Abstract This paper presents a methodology for estimating the fatigue life of elastomerlsteel flexelements that includes the effects of both mechanical fatigue loads and ageing of the elastomer. Previous methods calculated the rate of fatigue crack growth in the elastomer layers of flexelements using fracture mechanic analysis and a material fatigue model obtained from tests on new elastomer materials which ignored ageing. This workshows how elastomer ageing can be taken into account and the impact this can have on the calculated fatigue life. This methodology has been applied to the Design verification of the structural flexelements for the RamPowell TLP tendons to be installed in the Gulf of Mexico in 1997. The tendon flexelements carry the full tendon loads and provide near moment-free joints at the top and bottom of each tendon. The analysis can also be used for riser system flexelements and other elastomer steel layered structural components. The physical properties of elastomers change with age. The fatigue life of the Ram/Powell flexelement was Calculated to be 5160 years based on the properties of new Elastomer. When the properties of the ageing elastomer were taken into account, the calculated fatigue life ranges from 160 years to 400 years depending on the conservatism of the assumptions used. The effect of ageing is obviously significant. The analysis uses data generated from elastomer samples exposed to accelerated ageing conditions. A special purpose fracture mechanics program calculates the crack growth in each layer for each load in the yearly fatigue spectrum. The material properties are updated and total crack length is computed on a year-by-year basis until the failure criteria is reached. The present approach may remove some of the uncertainty associated with structural elastomer design, result in more realistic estimates of elastomer fatigue life, and may lead to the use of safety factors commonly associated with the design of more familiar structures. Introduction Flexelements are primary load bearing components of the tether system of tension leg and so it is of the Ram Powell TLP it was desired that a large safety factor be demonstrated. Previous work had developed and verified a fatigue analysis method for flexelements. This, however, ignored the effect of ageing of the elastomer with time, whereby the elastic shear modulus may increase and the fatigue resistance may decrease. Previous work had been based entirely on data from new elastomer material and did not include an ageing model in the fatigue calculations.