The reliability of suprapubic ultrasonography (SU) in assessing the size of the prostate was examined in 95 patients with benign prostatic hyperplasia (BPH). Volumetric measurements of the prostate and the transition zone of the prostate (TZP) performed by SU were compared with corresponding measurements obtained by transrectal ultrasonography measurements obtained by transrectal ultrasonography (TU). A very strong correlation was found between suprapubically and transrectally performed measurements for both the total prostate gland (r = 0.948, p < 0.001) and the TZP volume (r = 0.953, p < 0.001). According to the results of this study, SU appears to be reliable as TU in assessing the size of the prostate and the TZP and may be used effectively in the evaluation of patients with BPH, as it is less cumbersome, better tolerated, and a widely available examination technique.