Gray scale ultrasound can define intrarenal structures which could not previously be visualized. The normal calyces and infundibula within the renal sinus can be evaluated for abnormalities. Parenchymal anatomy (cortex, medulla, and arcuate vessels) of the right kidney is best demonstrated with the patient supine, using the liver as a window; anatomy of the left kidney is best appreciated using coronal scans in the right lateral decubitus position. Criteria and differential diagnosis of "Type I" parenchymal changes, in which the echo intensity within the cortex is increased, and "Type II" changes, in which there is a focal or diffuse disruption of normal renal parenchymal anatomy, are presented.