This paper describes an inverse methodology to ascertain the material properties of the tracheal cartilage of the leatherback turtle. The load-displacement history from the material testing of a tracheal cartilaginous ring is compared with that from a corresponding finite element analysis. Using constrained optimisation the square of the integral difference between the two load-displacement histories is minimised with respect to the material properties in the analysis. The properties in the optimised analysis are deemed to be reflective of those in the material testing. There is a high level of agreement between the results obtained from the material testing and those predicted by the analysis. ©Civil-Comp Press, 2011.