In the present study, we have demonstrated that the ectopic endometrial lesions showed a higher number of immune stained cells expressing cellular invasion markers (MMP-9 and its inhibitor TIMP-2) and of molecules involved in cellular proliferation and differentiation (MT and p63) than the eutopic endometrial lesions, using a rabbit experimental model of endometriosis. This evidence concerns the gene MMP9 and endometriosis.