Prostates of the same volumes were found to have very variable shapes, that is, combinations of variably elongated width, height, and lengths. These were believed to be possible causes of the differences in the severity of both the obstructions and symptoms in the prostates even when their volumes were similar. We measured the transverse (width), anterior-posterior (height) and longitudinal (length) diameters of the prostates and the transition zone, and their calculated volumes using transrectal ultrasonography. To establish the relationship between the International Prostate Symptom Score (IPSS) and each of the dimensional parameters of the transition zone and the total prostate, 105 consecutive patients (mean age 66.43 ± 9.24 years with a range o6f 46 to 90) who had voiding dysfunctions that were presumably related to BPH were analyzed using the t-test. Patients with conditions other than BPH were excluded. The results were as follows: 1. There was no significant correlation between the IPSS and any prostate volume parameter in the constant prostate volume conditions, because of the small numbers in each group. However, in the analysis of the total number of cases in all the volume categories, a significant correlation was found between the IPSS and some prostate dimensions; i.e., the longitudinal parameters in the total prostates (p < 0.01), and the transverse (p < 0.05) and longitudinal parameters (p < 0.05) in the transition zones. 2. Further investigations of the statistics of these significant parameters showed that prostates that were longer than 4 cm had significantly more severe symptoms than prostates shorter than 4 cm (p < 0.05), and that prostates with a ratio of length in the transition zone to the length in the total prostate ratio that was greater than 0.8 had significantly higher symptom scores than those with lower ratios (p < 0.05).