A 39-year-old male was admitted with fever, systemic lymph node swelling, liver dysfunction and mild splenomegaly. Liver biopsy specimen showed histiocytic aggregation in portal areas. These histiocytes were closely packed with granules, dyed sea-blue with May-Giemsa staining. Further microscopical examination of lymph nodes, gastro-intestinal tract and bone marrow also revealed the accumulation of sea-blue histiocytes. Activities of lipid metabolic enzymes were normal and hematopoietic diseases which are sometimes accompanied by secondary sea-blue histiocytosis were ruled out. We diagnosed this case as syndrome of the sea-blue histiocyte.