- 29 -AbstractThe present invention for the treatment of endometriosis relates to providing a parenteral dosage form (delivery system) for the controlled release of an aromatase inhibitor (AI) in a daily release rate that does not induce stimulation of the ovaries by negative feed back of the pituitary-ovarian-axis (which would cause secretion of gonadotropins and5 stimulation of ovarian follicular growth) and a gestagen in a daily release rate below the ovulation inhibition dose that provides contraceptive efficacy based on local effects (e.g. reducing and thickening of the cervical mucus impairing sperm ascension, effects on the endometrium and on tubal motility impairing implantation and egg transport).