A case is reported of idiopathic hypereosinophilic syndrome involving many organs and systems and with a wide range of clinical findings: hematologic, cardiovascular, skin, pulmonary, spleen, liver, and gastrointestinal. Mortality in such patients is very high, but aggressive medical treatment (vincristine 2 mg/week for 5 weeks) produced a significant clinical benefit and considerably improved our patient's prognosis.