Experience with 20 simple ureteroceles in 18 children is reviewed. In most cases hydroureteronephrosis of various grades of severity was present. In 5 cases the related kidney was non-functioning. The ureterocele generally is seen on excretory urography, either as a positive cobra-head dilatation or as a negative filling defect in the cystogram when renal function is impaired. Cystoscopy is diagnostic but confusion may occur when a lax ureterocele is compressed and emptied or even everted by a high intravesical pressure. Expectant management is warranted in the absence of upper tract dilatation but operative intervention is needed in most cases. Nephroureterectomy may be unavoidable if the kidney is afunctional. Simple unroofing or incision of the ureterocele is followed by vesicoureteral reflux and ascending infection. The preferred technique is total excision of the ureterocele and reimplantation of the ureter into the bladder by an antireflux technique.