The purpose of our study was threefold: to evaluate the ability of excretory phase CT urography to opacify the urinary collecting system by comparing opacification seen on CT with the opacification seen on a series of unmatched IV urography examinations; to determine the optimal CT urography technique for ureteral filling by comparing studies of patients who were imaged supine, prone, and with abdominal compression; and to assess the possible value that reformatted planar images might add to axial excretory phase images. Seventy patients with hematuria were imaged in one of four ways. Twenty-five patients underwent contrast-enhanced excretory phase helical CT of the kidneys, ureters, and bladder. All patients were imaged in a supine position. Ten other patients underwent a similar CT protocol in which we used abdominal compression. Ten further patients underwent excretory phase CT while in a prone position. A final 25 patients underwent IV urography. Each patient's collecting system was arbitrarily divided into 10 parts (both right and left sides of calices; pelvis; upper, mid, and lower ureters) for scoring of images on a five-point scale for opacification by contrast material. Opacification scores for the four groups of patients were then compared. For patients who underwent CT, reformatted images of the collecting systems were generated and evaluated for their potential to add value to the conventional axial images. We found no significant difference in the ability of CT urography and IV urography to yield opacification of the calices, pelvis, and upper or mid ureters. Opacification of the distal ureter was less well seen on supine CT urography than on IV urography. Prone and compression CT urography resulted in better opacification of the collecting system than the supine noncompression technique. Opacification of the distal ureter was best seen with compression CT and was as good as that seen with IV urography. Reformatted CT urography was judged to be of probable or definite additional value to the axial images in 44% of cases. In each case, we saw a pathologic finding whose relationship to the kidney and collecting system was not as easy to appreciate on the axial CT scans. CT urography with abdominal compression results in reliable opacification of the collecting system that is comparable with opacification seen on IV urography. In patients with abnormalities, reformatted images were a useful adjunct to axial images. CT urography has potential as an imaging tool for the urothelium.