Ultrasound (US) evaluation of the transplanted kidney is fairly simple because the graft is commonly placed in the retroperitoneal space of the right iliac fossa in a superficial position. Color or power Doppler is applied to evaluate the parenchymal flow and to identify the renal hilum and the anastomoses. The study is normally performed with a convex transducer with a variable frequency between 3.5 and 5 MHz. The US is the first, easy to apply, repeat, and easily accessible in posttransplant surgery evaluation and its complications. It allows the evaluation of parenchymal (acute tubular necrosis, transplant rejection, pharmacological toxicity, and infections), vascular (renal artery stenosis, renal infarct, renal vein thrombosis, arteriovenous fistulas, and pseudoaneurysm), urinary collector system complications (urinomas, urinary obstruction, and kidney stones), liquid collections (hematomas, lymphoceles, and abscesses), neoplasm, and recurrent renal diseases.