Endometriosis has long been thought mostly to affect the adult female population. However, awareness of possible endometriosis already in adolescence is now receiving increasing attention. It seems that certain markers in adolescence are associated with a subsequent diagnosis of the disease. These include chronic pelvic pain, severe dysmenorrhea, dysmenorrhea resistant to non-steroidal anti-inflammatory drugs and oral contraceptive pills, and pain interfering with daily activity. Based on current knowledge, it should be possible to diagnose endometriosis before adulthood, thereby alleviating symptoms and possibly limiting sequelae. To do so, knowledge of adolescent endometriosis has to be improved among both health professionals and the public.