Radical Retropubic Prostatectomy (RRP) is the choice treatment for localized prostate cancer. Transrectal ultrasonography (TRUS) was used to predict local tumor extension in ninety-one patients prior RRP. In these patients 41% showed histologic evidence of extracapsular spread. These data suggest that ultrasonography is associated with considerable staging errors when used to evaluate men with clinically localized prostate cancer.