We evaluated 53 patients with computerized tomography after renal transplantation. The diagnostic value of computerized tomography scanning was primarily in differentiating between patients with acute rejection and those with obstructive uropathy, urinary fistula or significant perinephric fluid collections. Computerized tomography guidance also may be helpful in performing anterograde pyelography or percutaneous allograft biopsy. The computerized tomography scan provides an effective, non-invasive, complementary method of evaluating post-transplant dysfunction.