The guidance of a computerized axial tomography scanner was used to locate the biopsy site in 10 instances where a previous attempt had failed to yield a satisfactory specimen. 4 of these patients were grossly obese, and the renal allograft could not be outlined by manual palpation. The scanner has facilitated the placement of the needle tip within the renal cortex, while avoiding injury to the renal pelvis, major blood vessels, and other intra-abdominal organs. Adequate tissue was obtained in each instance. There were no complications associated with this procedure. Proper use of this technique should enhance the success rate of needle biopsies and eliminate the need for open surgical biopsies in renal transplant recipients.