In this retrospective study, a review of the features of 21 recent cases of xanthogranulomatous pyelonephritis (XGP) is presented and compared with current published reports to improve the preoperative diagnosis. The clinical, laboratory, and radiological features, preoperative diagnoses, and operative methods of 21 patients with XGP were retrospectively reviewed. Mean age of the patients was 52.1 years; the female:male ratio was 2.5:1. All patients were symptomatic, and most common symptoms were flank pain and fever greater than 38 °C. The laboratory results showed anemia in 71.4% of cases, leukocytosis in 61.9%, and pyuria in 81.0%. In radiologic examinations, renal or ureter stone in 9 patients, hydronephrosis in 12 patients, a renal mass in 2 patients, and kidney enlargement in 9 patients were observed. For the patient who was suspected as having XGP before surgery, partial nephrectomy was performed; for 2 patients who were suspected as renal cell carcinoma, radical nephrectomy was performed; and for the remaining 18 patients, simple nephrectomy was performed. Among patients complaining of flank pain and fever, if the patients have a urinary tract infection and show the signs of anemia or leukocytosis and have staghorn calculi or a urinary tract obstruction and renal mass by radioactive examination, it is believed that the possibility of XGP should be considered.