The ovarian hyperstimulation syndrome is a complication of the controlled ovarian hyperstimulation in assisted reproduction procedures. It has become more widespread, since the techniques of ovarian hyperstimulation has become more frequent. The potentially life-threatening complication of this condition is a hemoconcentration with subsequent thrombo-embolic complications and death. In this article the pathophysiology, prevention strategies, treatment guidelines and more theoretical approaches for the therapy are reviewed and discussed.