This paper deals with the simultaneous identification of the four through-thickness orthotropic rigidities of a thick composite tube. A diametral compression test has been carried out on a glass/epoxy ring cut from the tube. The full strain field has been measured over one face of the sample with the grid method. The measured fields have been processed with the Virtual Fields Method to identify the rigidities of the material. At the beginning, discrepancies and significant variations occurred in the identified moduli due to inhomogeneous distribution of the strains through the thickness. A method based on a simultaneous measurement on both sides of the ring has been adopted. Very satisfactory results have been obtained using this methodology.