Hemophagocytic syndrome (HPS) is characterized by the activation of the mononuclear phagocytic system with prominent hemophagocytosis in the bone marrow and reticuloendothelial systems, and its occurrence is usually associated with variable disorders such as viral infections and malignant lymphoma. Recently, it was reported that HPS also occurred in association with underlying connective tissue disease, especially systemic lupus erythematosus. We report here a case of recurrent HPS complicated with systemic sclerosis. A 32-year-old woman had been diagnosed as systemic sclerosis since 1994. She was admitted due to unknown high fever and severe pancytopenia in 1997, and the diagnosis of HPS was determined because of hemophagocytosis in bone marrow and hyperferritinemia. Her symptoms were improved by immunosuppressive therapies including steroid pulse therapy and oral prednisolone (60 mg/day). She was followed by the treatment of oral prednisolone which was gradually tapered in our out-patient clinic. In August of 1999 high fever and severe anemia were recurred, and she was admitted again to our hospital because of the diagnosis as recurrent HPS. She had been treated with 40 mg/day of oral prednisolone and fever was immediately disappeared and hemoglobin was gradually increased. HPS is considered to be a rare complication with systemic sclerosis, and the etiology has been unknown. IL-18 is a novel cytokine which is a potent inducer of interferon-gamma, and its properties may be a proinflammatory regulation and activation of monocyte/macrophage and histiocyte through the expression of interferon-gamma. Therefore, the significance of IL-18 in the pathophysiology of HPS was recently reported. In this case, we investigated the significance of IL-18 and revealed the levels of serum IL-18 were well correlated with disease activity of HPS.