Endometriosis can occur in women of any age who have started their menstrual periods, typically between the ages of 10 and 45. However, endometriosis is more commonly diagnosed in women in their 30s and 40s. It is possible for endometriosis to occur in girls who have not yet started their periods, although this is rare. Endometriosis may also develop after menopause in some cases, although this is less common. Therefore, there is no specific age limit for endometriosis.