Although visualization of the genitalia on Tc-99m DTPA transplant renography has been reported previously, its frequency and clinical significance have not been fully evaluated. The authors conducted a retrospective evaluation of 153 renal transplant scintigrams obtained in 129 patients during a 2-year period. The results showed that significant genital blood pooling occurred in nearly 50% of studies. Because the finding was commonly associated with little or no radioactive urine in the bladder, as in acute tubular necrosis or poor graft function, exaggeration of the normal blood pool was thought to be the possible cause for its occurrence. It is, however, important to distinguish genital blood-pool activity from the bladder with radioactive urine to avoid making an incorrect diagnosis.