Tosagestin (Org 30659) is a synthetic 19-nortestosterone derived progestogen. It was under clinical development by NV Organon for use in oral contraceptive and hormone replacement therapy. After oral administration of [14C]-Org 30659 to postmenopausal women, the compound was extensively metabolized. The dosed radioactivity was predominantly excreted via urine. Org 30659 was to a large extent metabolized at the C3- and the C17-positions. Species comparison of the metabolic routes of Org 30659 after oral administration indicated that the monkey seems to be a better representative species than the rat for the metabolism of Org 30659 in humans. Daily oral administration of Org 30659 suppresses ovarian function to a level sufficient to inhibit ovulation. This effect is dose-dependent, and the suppressive effect is readily reversible at all doses tested. Tosagestin had been in phase II clinical trial for the treatment of the menopausal syndrome. However, this development was discontinued.