Twelve cases of Wilm's tumor were examined: By intravenous pyelography alone in eight children and by pyelography and angiography in four adults. Intravenous pyelography showed characteristic displacement of the calyceal structures and displacement of the renal pelvis. Angiography gave detailed information regarding the vascular supply to the mass, the degree of vascularity, presence and number of tumor vessels and degree of pooling of contrast material in the tumor. Vascular penetration through the capsule of the kidney was not always consistent to perirenal tumor infiltration. By angiography one case of bilateral Wilm's tumor and two cases with metastases were discovered.