Transrectal ultrasonography was performed in 121 patients with the chronic prostatitis syndrome (CPS), and in 20 patients with urological pathology not involving the prostate gland. The ultrasonographic aspects of the seminal vesicles (SV) in normal subjects and in patients with the CPS are described. In the latter group, characteristic ultrasonographic patterns can often be obtained, even in patients affected by prostatodynia, in whom all the other clinical and laboratory findings were absent. They consisted of: (a) dyshomogeneous echo-structure of the prostate; (b) constant dilatation of the periprostatic venous plexus, greater than 150 mm2; (c) dilated, elongated SV, with thickening of their inner septa (they are sometimes asymmetrical), and (d) bladder neck hypertrophy.