A case of ovarian fibrosarcoma producing multiple cytokines is presented. The tumor occurred in the left ovary of a Japanese woman with epigastralgia, remittent fever, leukocytosis and slight thrombocytosis with moderate increase of mast cells in bone marrow, but lack of hormonal abnormality. The resected tumor of the ovary was well encapsulated and it was composed of spindle-shaped tumor cells and scattered tubules with marked mast cell infiltration. The tumor recurred in the pelvic cavity 14 months later, accompanied by similar signs and symptoms as occurred with the primary tumor. Serum levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha were elevated. The recurrent tumor showed similar histological findings to those of the primary tumor, except for lack of tubules. Tumor cells revealed a focally positive immunoreaction for vimentin, IL-6 and TNF-alpha and alpha-inhibin. Reverse transcription-polymerase chain reaction using total RNA obtained from the recurrent tumor demonstrated mRNA expression of IL-6, IL-10, TNF-alpha and stem cell factor. This is a rare case of ovarian fibrosarcoma producing multiple cytokines, resulting in atypical clinical findings.