A case of bladder tumor producing granulocyte colony-stimulating factor (G-CSF) is reported. A 78-year-old male presented with macroscopic hematuria. Cystoscopy demonstrated a large bladder tumor. Drip infusion pyelography and computerized tomography of the chest, abdomen and pelvis revealed right hydronephrosis, but did not reveal any metastasis. Total cystectomy and construction of bilateral cutaneous ureterostomy was performed. Histologically, the tumor consisted of sarcomatoid carcinoma with foci of transitional cell carcinoma (G3 > G2), showing marked infiltration of polymorphonuclear leukocytes. Immunohistochemical examination revealed a high concentration of G-CSF in the tumor specimen. Preoperatively, the white blood cell, count in the peripheral blood and serum G-CSF concentration were elevated, 45,400/mm3 and 73.4 pg/ml, respectively. After surgery these values became normal. This is the 19th reported case of G-CSF producing bladder tumor in Japan. The prognosis of the reported cases of G-CSF producing bladder tumor has been very poor. Fourteen of the reported 19 cases died within one year. This patient should be carefully followed up.