The authors present their experience with the severe ovarian hyperstimulation syndrome when they were using stimulation for IVF and ET and they compare it with the literature. Over a period of 23 months. 154 stimulations were carried out using a long protocol associated with a CnRH agonist and hMG. 142 vaginal aspirations were carried out. The clinical pregnancy rate was 19% per aspiration and 21.9% per transfer. Of the 142 patients who were aspirated five had severe ovarian hyperstimulation with a favourable outcome. The authors suggest a physiopathological comparison for ovarian hyperstimulation and the management to be carried out when this complication occurs. They emphasise how potentially serious this complication is and that there has been no physiopathological explanation for its recrudescence since GnRH agonist have started to be used.