Nowadays, oxygen-ozonetherapy is used in many chronic inflammatory diseases, especially in orthopedics, neurology, and infectious diseases. Recent studies have confirmed that oxygen-ozonetherapy could be used in urology and gynecology to treat inflammatory conditions and infections. We intend to understand if oxigen-ozone systemic therapy applied to In Vitro Fertilization (IVF) could improve pregnancy outcomes. We present three cases of long-term primary infertility with previous implantation failures suffering from endometriosis or adenomyosis. Before the embryo-transfer, the patients were treated with a 2/3-month course of Gonadotropin-Releasing Hormone Agonist (GnRHa) combined with 3-4 sessions of oxygen-ozone systemic therapy. We combined a mixture of oxygen and ozone, with ozone concentrations ranging from 30µg to 45µg, increasing the dosage at each session. The oxygen-ozonetherapy session started during the hormonal endometrial preparation and stopped 1-7 days before the embryo-transfer. All the patients were also treated with intravenous vitamins. In all our patients, we obtained a positive blood ?- Human Chorionic Gonadotropin (hCG) test and an ongoing pregnancy