The ovarian hyperstimulation syndrome (OHSS) is an iatrogenic, unpredictable and potentially life-threatening complication in patients submitted to pharmacological ovarian stimulation. Information on risk factors, etiopathogenetic mechanisms, prevention strategies and therapeutic management is continuously updated. The present study retrospectively analyzed 123 women affected by different grades of OHSS as a result of pharmacological ovulation induction. Hospital admission was suggested in 14 patients with severe OHSS, whereas patients with moderate or mild OHSS were followed in the out-patient section of our department. The results confirmed the efficacy of the therapeutic scheme adopted. The syndrome is localized to the ovaries at the time that the condition is triggered; when organs different from the ovaries become involved, OHSS assumes systemic aspects. The different clinical signs are the basis of a proposal of a local and systemic classification.