Ovarian hyperstimulation syndrome (OHSS) is the most serious iatrogenic complication associated with ovarian stimulation. It is only in recent years that the understanding of OHSS has advanced sufficiently to develop treatment options aimed at reducing the incidence and effects of OHSS. Currently, there is no good test or method for identifying susceptible patients. Nevertheless, progress has been made in the prevention of OHSS. Physicians have a wide range of treatment options, including coasting, re-initiation of a GnRH antagonist, and application of agonists, like dopamine in the luteal phase or triggering oocyte maturation with a bolus of GnRH agonist. These treatments, together with other procedures, like oocyte/embryo vitrification, have allowed physicians to improve the prediction and prevention of OHSS.