The use of controlled ovarian hyperstimulation has increased the efficacy of ovulation induction and enhanced the ability to recruit multiple mature oocytes for use in the assisted reproductive technologies. However, the administration of medications is not without risk. Ovarian hyperstimulation syndrome is a serious complication with various manifestations. Two fundamental pathologic changes are characteristic: ovarian enlargement with underlying stromal oedema and multiple haemorrhages of luteinized cysts coupled with a dramatic shift of fluid from the intravascular spaces into the peritoneal, pleural, and pericardial cavities. The most efficacious treatment of hyperstimulation syndrome is its prevention. The correction of hypovolaemia and electrolyte abnormalities is one of the most important procedures in the treatment of this syndrome.