A combined numerical±experimental method for the identi®cation of six elastic material modulus of generally thick composite plates is proposed in this paper. This technique can be used in composite plates made of di erent materials and with general stacking sequences. It makes use of experimental plate response data, corresponding numerical predictions and optimisation techniques. The plate response is a set of natural frequencies of¯exural vibration. The numerical model is based on the ®nite element method using a higher-order displacement ®eld. The model is applied to the identi®cation of the elastic modulus of the plate specimen through optimisation techniques, using analytical sensitivities. The validity, e ciency and potentiality of the proposed technique is discussed through test cases. Ó