Transabdominal ultrasound is superior to excretory urography when radiographic imaging of the urinary tract is indicated in patients with prostatism. We studied 53 patients with excretory urography and ultrasonography before prostatectomy. Patients with a history of microscopic or macroscopic hematuria, urolithiasis, renal failure or upper urinary tract anomalies were excluded from our study. Ultrasonography proved to be more accurate in defining prostatic size and configuration. Bladder wall thickness also was quantified more clearly with ultrasonography. We found 17 renal masses incidentally with excretory urography, although ultrasound was essential and superior to excretory urography in defining these masses in each case. We recommend that ultrasonography be used in lieu of excretory urography when imaging of the urinary tract is indicated before prostatectomy.