Parameters of prostate volume and shape were determined in a community based population of 502 men 55 to 74 years old who had not undergone a previous prostate operation and did not suffer from prostatic cancer. The volumes of the total prostate and of the central relatively hypoechoic area of the prostate were determined. Of all men in this age range 95% had a total prostate volume of more than 20 cm3. Moderate correlations between age and both volume measurements were found (r = 0.26, p < 0.0001 and r = 0.34, p < 0.0001, respectively). The percentage increase per year of central hypoechoic volume (3.5%) was higher than that of total prostatic volume (2%). The average doubling time of total prostatic volume and volume of the central hypoechoic prostate was calculated to be 35 and 20 years, respectively. The roundness of the prostate as expressed by width-to-height ratio at the largest transverse section of the prostate correlated poorly with age (r = -0.13, p = 0.004). The average total prostate volumes as measured by transrectal ultrasound were 21 to 28% higher than reported average volumes measured at autopsy in men in the same age range.