The nuclear factor kappaB (NF-kappaB) is a ubiquitously expressed transcription factor playing vital roles in innate immunity and other processes involving cellular survival, proliferation, and differentiation. This review highlights the importance of NF-kappaB in the pathophysiology of endometriosis. Constitutive activation of NF-kappaB has been shown in endometriotic lesions. Complex interactions of NF-kappaB with steroid receptors and apoptotic molecules in endometriosis resulting in opposing roles of NF-kappaB are discussed. NF-kappaB regulates the expression of cytokines mediating autocrine self-amplifying cycles of cytokine release and NF-kappaB activation, leading to maintenance of inflammatory reactions in endometriosis. NF-kappaB can contribute to the increased ability of endometriotic cells to invade and adhere to the peritoneal surface by regulating the expression of matrix metaloproteinases. We are presenting the role of NF-kappaB to regulate vascularization and oxidative stress in endometriotic cells. Effects of drugs used for the treatment of endometriosis on NF-kappaB pathway are presented and we show how drugs that inhibit the NF-kappaB can mediate the progression of endometriosis. Novel therapeutic strategies involving the NF-kappaB and applied in endometriosis are also discussed.