Congenital seminal vesicle cysts represent a rare but illustrative type of embryological malformation. They often are combined with ipsilateral upper urinary tract abnormalities. In most of the cases described in the literature the diagnosis has been made with rather invasive procedures. On the basis of our experience with 3 cases we recommend pelvic ultrasonography as the initial study in patients in whom such a malformation is suspected. Although other radiological procedures may be required to confirm the diagnosis, this approach appears to be cost-effective and accurate in most instances. The treatment of such malformations should be restricted to symptomatic cases and usually consists of vesiculectomy with or without removal of the ipsilateral dysplastic or hypoplastic kidney.