Disclosed is an apparatus and method for the treatment of the symptoms of obstructive prostatism. The apparatus comprises an expandable dilation catheter and preferably an axially elongate sheath, adapted for transurethral insertion via the external opening of the urethra. The sheath is ellipsoid in cross-section, and provides an initial path through which the catheter and a standard cystoscope lens is guided. The dilation catheter or the sheath are provided with a non-radiological locating means for positioning the dilation portion of the catheter with respect to an anatomical landmark. Once the catheter has been properly positioned with respect to both the bladder neck and the sphincter, the dilation balloon may be inflated to force open the affected prostatic urethra and eliminate the obstruction.