Endometriosis is a disease that imposes a severe financial burden on society, and a physical and emotional toll on people who have it. Therefore it is important to understand, and education by medical staff against this disease. According to the statistics service approximately 200 women a year are treated in reproductive age of which on average 50 are endometriomas and since there is no clear scientific evidence on the impact of combined oral contraceptives compared with using Dienogest, the objective of this study is to determine the impact of Dienogest to 2 mg / day compared with combined oral contraceptives (levonorgestrel + ethinyl estradiol) in reducing the size of the endometriomas diagnosed by transvaginal ultrasound in women with diameters smaller than 4 centimeters thereof, in the Hospital Universitario Fundación Santa Fe de Bogota.