We report two cases of granulocyte-colony stimulating factor (G-CSF) producing infiltrating urothelial carcinoma of the kidney. Case 1: A 58-year-old woman was referred to our hospital for fever and right back pain. Blood test showed severe inflammation and computed tomographic (CT) scan demonstrated swelling and irregular enhancement of the right kidney. Under the diagnosis of pyonephrosis or renal tumor, we performed right radical nephrectomy. The patient died of lung and liver metastases 6 months postoperatively despite of adjuvant chemotherapy. Case 2: A 76-year-old woman was referred to our hospital for a chief complaint of gross hematuria. Retrograde pyelogram and CT scan demonstrated a right renal pelvic tumor and we performed right nephroureterectomy. The patient died of liver and lung metastases 4 months postoperatively. The pathological and histochemical findings of these two cases were G-CSF producing infiltrating transitional cell carcinoma of the kidney. They showed marked leukocytosis and elevation of serum G-CSF levels. To our knowledge, they are the first two cases of G-CSF producing infiltrating urothelial carcinoma of the kidney in Japanese literature.