We evaluated the changes in volume of the seminal vesicles as determined by transrectal sonography in terms of the possible relationship with aging, lower urinary tract symptoms and benign prostatic hyperplasia (BPH) in community based populations in Japan. In 641 men (55-86 years, mean 67) on a mass screening program for prostatic diseases, the maximum horizontal area of the seminal vesicles (MHA) was compared with age, American Urological Association (AUA) symptom index scores and transrectal ultrasonic parameters of the prostate including prostatic volume, transition zone (TZ) volume, TZ index and presumed circle area ratio (PCAR). Simple regression analyses demonstrated that MHA correlated significantly with age, prostatic volume, TZ volume, TZ index and PCAR, but not with AUA symptom index scores. Multiple regression analysis revealed age, prostatic volume and PCAR to be independent determinants of MHA. There was a difference in MHA between subjects with BPH (7.1±2.5 cm²) and those with a normal prostate (5.6±2.1 cm²) with a statistical significance. In the morphological evaluation of the seminal vesicles, the significant influence of age and BPH has to be taken into account.