OBJECTIVE To determine the significance of gray scale ultrasound as a tool for diagnosis, follow-up and treatment of urological complications of renal transplantation based on the experience of our institution. METHODS A retrospective, longitudinal and observational study was carried out. We reviewed the patients' perioperative ultrasound scans and their respective urological complications from January 1, 1982 to January 1, 2000. The patients were consecutively taken from the kidney transplant registry of the Urology and Nephrology and Transplant Departments. We describe the ultrasound findings of normal functioning grafts as well as those with urological complications, such as fluid collections (lymphocele, hematoma, urinoma and abscess), uronephrosis and its possible causes, and symptomatic vesicourethral reflux. CONCLUSIONS Diagnostic and therapeutic algorithms in kidney transplant patients have been changed since the advent of ultrasound in our country in 1981. Rapid diagnosis and better therapeutic options have been the hallmarks of ultrasound. Added advantages are: it is low-cost, non-invasive, not time consuming. It can be performed regardless of kidney function, can be repeated as many times as required, subsequent scans can be compared. It can be carried out in special care units. The superficial location of the graft makes it highly sensitive. Its disadvantages are low specificity to identify either the nature of the fluid collections or the precise site of urinary tract obstruction, apart from depending on the skill of the operator. Specialists should be familiar with the surgical anatomy of the kidney graft and its variations in order to utilize completely its diagnostic and therapeutic potentials.