Since the correlation between the amount of Ethinylestradiol (EE) and the thromboembolic risk has been recognized, the development of new oral contraceptives (OC) has been characterized by a constant lowering of the EE dosage. The consecutive decrease of ovulation inhibition has been compensated by the introduction of potent progestagens. Therefore, the contraceptive safety has been maintained in presence of less side-effects. The effect of ultra-low-dose OC on acne and seborrhea remains beneficial. The effect of ultra-low-dose OC on bone is contradictory. Because there are fundamental differences between Estradiol and EE, the thromboembolic risk is not decreased by the parenteral administration of EE. In users of the contraceptive patch, it is even increased. EE is not bound at SHBG. Because of its Ethinyl group, the inactivation of EE occurs slowly. Therefore, EE reaches the liver in a low but constant concentration where it modifies many estrogen-dependent hepatic parameters significantly. One of these is hemostasis. It is generally accepted that such changes are responsible for the increased thromboembolic risk of the contraceptive patch and vaginal ring. A reduction of the hormone-free interval of the pill to 5 or 4 days results in a complete suppression of the ovarian function, a reliable ovulation inhibition and an increase of the contraceptive efficacy in spite of a reduction of the EE dosage to 20 microg or 15 microg.