The differential diagnosis of anuria in the newborn over 24 hours of age includes severe renal dysplasia and complete urinary obstruction. The latter is rare, but may be correctable. When it is reasonable to expect that significant information can be gained, aortography is indicated and feasible even in a premature infant. The use of angiography to establish the diagnosis of bilateral renal agenesis in a 1,785 gm. infant is reported.