A non-interventional, observational program to assess the effects of oral dydrogesterone therapy in a post-marketing setting whether the effects are related to the regimen of dydrogesterone therapy. In this observational program, assuming that dydrogesterone plays a role in the treatment of endometriosis without suppression of ovulation, the goal is to observe the possible implications of such treatment in terms of treatment regimen and response pattern. In the study will be described effects of Duphaston® 6-months-administration in patients with confirmed endometriosis by assessing pain relief, quality of life, need of self-medication with analgesics, etc.