A total of 420 sonograms of renal transplants in 80 children were obtained because of decreased renal function or to establish a baseline after surgery. We describe normal anatomy of a renal transplant on sonograms, including duplex Doppler and color flow images, and a spectrum of complications. The complications are categorized as follows: parenchymal (drug toxicity rejection, acute tubular necrosis, infection), vascular (pseudoaneurysm, arteriovenous fistula, renal artery stenosis and occlusion), obstructive uropathy, and postoperative fluid collections.