Medical treatment of endometriosis has been applied since 40 years. Its rational is based upon the hormone-dependency of the endometriotic lesions inducing a resting status. Adhesions, endometriomas or fibrous sequellae do not respond to medical treatment. Its use in case of associated infertility is very limited. Numerous agents are available for clinical use. Progestins are efficient on pelvic pain, contra-indications, clinical and metabolic tolerance are linked to the hormonal activity of the molecules. They have a low cost. Newer pills deserve to be evaluated. Danazol has now few indications in regards to its clinical and metabolic side-effects. Gn-RH analogs bear a potent efficacy and a very low intrinsic toxicity. They are preferentially used in severe cases, in association with surgery and before an IVF. Add back therapy improves the clinical tolerance and reduces bone mass loss. Many parameters should be taken into account when selecting a specific modality.