Rinsing cumulus oophorus after oocyte retrieval is routinely performed in our department in Lyon for in vitro fertilization procedures when ovarian endometriosis is suspected. The aim of this procedure is to remove factors which might alter oocyte and embryo quality and fertilization and pregnancy rates. These factors, such as Tumor Necrosis Factor alpha (TNFalpha) and reactive oxygen species are known to be surexpressed in endometriosis. Their effect is not exclusively on the development of the oocyte and embryo but also on fertilization and implantation. It has been demonstrated that peritoneal and follicular fluid contains some factors that interfere with effective gamete interaction, as it has been determined by an in vitro animal assay. Peritoneal fluid from patients with mild endometriosis has an increased activity of TNFalpha, interleukin-1 (IL-1), antibodies and reactive oxygen species. This observation might be of importance in explaining subfertility associated with early stages of endometriosis. Cumulus-oophorus rinsing after oocyte retrieval might help to remove these deleterious factors. IVF outcomes in women affecting by endometriosis seem to be similar after cumulus-oophorus rinsing, as compared to those of patients undergoing IVF for tubal-factor infertility. This rinsing procedure could also be usefull in women affected by unexplained infertility: peritoneal and follicular fluid of these women contains increased levels of TNFalpha and reactive oxygen species, like women affected by endometriosis.