Clinical, radiological and ultrasonographical features of three cases of xanthogranulomatous pyelonephritis, one of which in a child, are reported. Presurgical diagnosis of xanthogranulomatous pyelonephritis is difficult and infrequent to date (10-14% of cases according to different workers). This complaint is generally mistaken for other types of kidney infections or tumours. The use of ultrasonography and computed tomography in particular help recognition of the disease and above all help to assess its extra-renal spread: something that has only recently been made possible.