PURPOSE: To evaluate the prevalance of morphological variation of the kidney secondary to junctional parenchyma, as well as to analyze the ultrasonographic features of junctional parenchyma. MATERIALS AND METHODS: Two hundred and eighty two kidneys of 141 patient without clinical or radiologic evidence of renal disease were prospectively analysed using ultrasound. In all patients, ultrasonograms were obtained in sagittal, coronal and transaxial planes. The kidney was considered to have morphological variation if the ulrasonogram demonstrated junctional parenchymal defect or line ; those showing such variation were classified as one of three types :continuous, discontinuous, or junctional parenchymal line or defect without junctional parenchyma. The prevalance and ultrasonographic features of the kidneys were evaluated. RESULTS: Morphological variation was noted in 71 cases(25%). the continuous type accounted for 54% of these, the discontinuous type for 38%, and junctional parenchymal defect or line without junctional parenchyma for 8%. In all cases, junctional parenchyma was located approximately at the junction of the upper and middle third of the kidny, and had the same echogenecity as the renal cortex. CONCLUSION: An understanding of the morphological variation of the kidney resulting from junctional renal parenchyma would be helpful in differentiating pseudo tumor from true renal neoplasm.