Longitudinal and radial transrectal prostatic ultrasound techniques were compared for their consistency and reproducibility in recording prostatic size. While the longitudinal image at the 12:00 position was consistent, radial scanning was variable depending on whether the apex, mid, or base aspects of the prostate were scanned. It is recommended that protocols requiring serial measurements of prostate size utilize a longitudinal ultrasonic transducer and scan at the 12:00 position.