Based on a report of 16 patients, the authors describe and evaluate the sonographic aspects of renal inflammatory diseases (RID) in children. In acute disease, thickening of the renal pelvic wall as evidence of pyelitis was the most common pattern demonstrated. Increased renal volume, nontumoral parenchymal area of hyperechnogenicity, abscess-type mass or calcified solid mass (in the case of xanthogranulomatous pyelonephritis) were other aspects encountered. Related findings included evidence of chronic pyelonephritis (cortical thinning) and of renal malformations. In patients with RID, the role of ultrasound is doubly important. While it is being employed increasingly as a screening test, it is most useful as a follow-up technique to detect complications and assess renal growth. Nevertheless, it should be stressed that ultrasound may be totally normal in cases of RID and complementary examinations (IVP, VCUG and nuclear scanning) are still necessary.