Ultrasound examination of a renal transplant was performed in 27 patients over a period of 28 months; there were kidneys from 12 living and 15 cadaveric donors. The ultrasonic scans were performed over a period ranging from 2 days to 12 years following transplantation. We were able to observe and describe the echographic findings of the normal evolution of a well functioning renal transplant, acute tubular necrosis, acute and chronic rejection, perirenal fluid collection, and obstructive uropathy. Ultrasound evaluation of renal transplant was accurate in the diagnosis of postoperative complications together with clinical and laboratory findings. Ultrasound imaging is independent of renal function and can be performed quickly as often as necessary. Percutaneous procedures, including fine needle aspiration, biopsy, aspiration of fluid collection, and positioning of the pyelostomy catheter can be performed under ultrasonic guidance.