A 36-year-old man presented with fever and right backache. Abdominal computed tomographic scan revealed a right renal cyst, with a maximum diameter of 12 cm, and surrounded by a hyperdense area of perirenal fat tissue. The cyst appeared to be infected. Accordingly, we performed a percutaneous puncture of this cyst, and drained the fluid. The brown and cloudy fluid gradually became clear, the fluid volume increased a few days after the drainage. A communication between the infected cyst and urinary tract was suspected ; retrograde pyelography confirmed the presence of fistulas. The urine was drained, ＞ 600 ml per day, for four weeks. Surgical resection of the cyst wall and closure of the fistulas were performed as an additional treatment. A year after the open surgical procedure, the renal cyst did not recur, and his renal function has been normal.