The Ovarian Hyperstimulation Syndrome (OHSS) is an iatrogenic complication of ovarian stimulation occurring during the luteal phase or during early pregnancy.It was appeared to be a possible complication of the induction of ovulation by almost every agent used for this purpose.The most common form occurs a few days after follicular rupture or puncture, when follicular growth has been medically induced by using either clomiphene citrate or gonadotrophins.Ovarian hyperstimulation syndrome is thought to result from increase in capillary permeability of the mesothelial surface, which leads to a depletion of intravascular volume and its secondary hemodynamic consequences.To minimize risk of OHSS, endogenous pregnancy- derived hCG may be eluded by judicious cryopreservation of all embryos.Treatment of acute phase relies only on an empirical and symptomatic approach. The general approach will be adapted to the level of severity. Specific approach such as paracentesis, pleural puncture and surgical treatment are included in line of treatment.