Nephrotomography was performed in 5 cases of renal adenoma, 4 of which were avascular. The single vascular lesion could not be differentiated from a solid hypernephroma. The major feature that distinguishes an avascular renal adenoma on ne-phrotomagraphy is the surrounding thick smooth capsule. This finding makes it possible to differentiate this potentially malignant lesion from a simple benign cyst.