Objective: To present our experience and the current knowledge about pathophysiology, diagnosis, and management of the ovarian hyperstimulation syndrome (OHSS). Design: Retrospective study concerning clinical and laboratory findings of severe OHSS. Setting: General ICU at a maternity-surgical hospital. Patients: Ten patients suffering from severe OHSS. Interventions: Supportive and preventive therapeutic measures applied are described. Measurements and results: Admission and discharge data as well as worst values during disease course were recorded. Clinical and laboratory findings showed third space fluid shift leading to weight gain, generalized tissue edema, ascites, hydrothorax, abdominal distension and pain, chest discomfort, hypovolemia, dehydration, ovaries enlargement, electrolyte disturbances, hypoalbuminemia, high hematocrit, urea, and WBC. Conclusions: OHSS is an iatrogenic complication of assisted conception of unknown pathogenesis, with potentially life-threatening sequelae due to hemoconcentration such as circulatory shock, ARDS, hepato-renal failure, thromboembolic phenomena, and multi-organ dysfunction syndrome. Gynecologists and intensivists must be aware of the diagnosis and management of the syndrome because of the widely used reproductive techniques for assisted conception.