Fifty patients without pelvic pathology were studied in order to determine the normal appearance of the seminal vesicles on computed tomography (CT). The seminal vesicles could be identified in all patients. The mean length of each seminal vesicle was 3.1 +/- 0.5 cm and the mean width was 1.5 +/- 0.4 cm. Calculated areas of the seminal vesicles assuming an ellipsoid shape were 3.6 +/- 1.1 cm2 for each side. When correlated with patients' ages, no significant difference was identified between age and the length of the seminal vesicles, however, a significant difference was noted between the widths (P less than 0.01) and areas (P less than 0.05) of the seminal vesicles with patients of increasing age having smaller seminal vesicles. In 67% of patients these structures were symmetrical and in 33% some degree of asymmetry was noted. Variability in shape ranged from ovoid (70%), tubular (20%), and rounded (10%). In 48 of 50 patients, small punctate densities could be seen along the lateral aspects of both seminal vesicles which correspond to the anatomic region of the pudendal venous plexus.