Most fungal infections of the urinary tract involve the drainage structures rather than the kidney parenchyma. They usually occur in patients with diabetes or other chronic debilitating diseases and in the presence of urinary stasis. Conglomeration of fibrillar hyphae results in fungal balls which produce nonopaque filling defects in the renal pelvis, ureter, or bladder. Such fungal ball colonies were demonstrated by percutaneous (antegrade) pyelography in the upper urinary tract in two cases. A percutaneous nephrostomy was performed in one patient to provide drainage of pus in the renal pelvis.