The function of the ureter is to transport urine from the renal pelvis toward the bladder and to protect the renal parenchyma from distally generated backflow and back pressure. The ureter manifests peristaltic activity and can adapt its mechanical characteristics to diuresis amount. The changes in ureteral function resulting from obstruction are dependent on the degree and duration of obstruction. Even the rate of urine flow, the mechanical and anatomic properties of the ureter, the nature of disease process and the age of the patient influence the response of the ureter to obstruction. It is the purpose of this report to correlate the anatomic and physiologic properties of the ureter with normal and pathologic clinical situations.