Peritoneal endometriosis is a chronic inflammatory disease characterized by increased numbers of peritoneal macrophages and their secreted products. Inflammation plays a major role in pain and infertility associated with endometriosis, but is also extensively involved in the molecular processes that lead to peritoneal lesion development. Peritoneal oxidative stress is currently thought to be a major constituent of the endometriosisassociated inflammatory response. Excessive production of reactive oxygen species, secondary to peritoneal influx of pro-oxidants such as heme and iron during retrograde menstruation, may induce cellular damage and increased proinflammatory gene expression through nuclear factorkappa B activation. In particular, prostaglandin biosynthetic enzyme expression is regulated by this transcriptional factor, and increased peritoneal prostaglandin concentrations have been demonstrated in endometriosis. In the light of available data collected from patient biopsies, as well as in vitro and in vivo studies, the respective involvement and potential molecular interactions of iron, nuclear factor-kappa B and prostaglandins in the pathogenesis of endometriosis are explored and discussed. The key role of peritoneal macrophages is emphasized and potential therapeutic targets are examined.