Twenty-four patients with suspected renal trauma have been studied by renal angiography. Each patient was initially classified as having suffered minor or serious kidney injury based on findings at abdominal roentgenography, intravenous urography and retrograde pyelography (if done). Any of the following findings classified a case as one of serious injury: extravasation of contrast medium, absence of excretion at time of intravenous urography, and diminution or obliteration of kidney outline or of the psoas line where these features could be evaluated. Ten of the 24 patients were classified as cases of minor injury; 9 showed normal angiograms and the other patient's angiogram demonstrated minimal or debatable changes of no great consequence. Fourteen cases were initially classified as serious kidney injury; 12 of these had positive angiograms. Thus, renal angiography need not be part of the diagnostic work-up of all patients with suspected renal injury, but only in those classified as "serious injury" as described here. The major angiographic findings were: thrombosis of the main renal artery; block of a major branch artery; non-filling of small peripheral arterial branches; arteriovenous fistula; localized displacement of peripheral vessels; underlying major renal disease; and vascular changes due to parenchymal damage after renal rupture. The relative significance of these findings in respect to the severity of kidney damage has been exemplified in the case reports. Emphasis is placed on the occurrence of vascular thrombosis and arteriovenous fistula resulting from renal trauma and on the important contribution of renal angiography to the proper evaluation of such patients.