AbstractThirty‐eight nephrectomy specimens and two biopsies of perinephric abscesses from patients with xanthogranulomatous pyelonephritis have been examined. Twenty showed evidence of venous damage. This included organised thrombi in 12, intimal thickening in five and phlebitis in three. All specimens showed evidence of previous haemorrhage in the form of haemosiderin deposition. These findings differed significantly from a control series of chronic pyelonephritis.It is suggested that venous occlusion and haemorrhage are factors in the pathogenesis of the lipid accumulation in the kidney which is characteristic of this condition.The association of a papillary transitional cell carcinoma of the pelvis in a patient with xanthogranulomatous pyelonephritis is reported for the first time.