Objective: To investigate the pathogenesis, exact nature, histologic feature of xanthogranulomatous interstitial nephritis (XGIN) as well as its significance in clinical medicine.Methods: The medical histories concerned were collected with diagnostic images including CT scanning,ultrasonography, intravenous urography ( IVU ) and laboratory data being synthesized by comparison with what was discovered during operations and pathologic examinations.Results: All patients were ever struck on their loins or backs by blunt violence over 4-12 years. The diseases were dinically diagnosed as "renal cancer" before, during and after operations, and treated with radical nephrectomy. Located at cortical parts, the tumor focus had penetrated the renal capsules and invaded other organs. However, immunohistochemistry demonstrated that the lesions were xanthogranulomas, not tumors, in which there were stacks of foam cells and lymphocytes with vast extends of fibrotic tissues obliterating the cortical interstitial structures. Urinary tracts yielded no bacterium,obstruction or calculus.Conclusions: XGIN is likely to be one kind of immunologic mediated granuloma following blunt renal trauma. It is imperative to clarify pathogenesis and character of this lesion so as to find out any approach to diagnosis and cure of such an unusual nephropathy.