A controllable sheath for optimizing the control of surgical instruments at the operation site includes a flexible sheath surrounding an endoscope and including a lumen extending along the walls of the sheath and adjacent to the endoscope. The lumen permits the passage of surgical instruments from the proximal end of the endoscopic device to the operation site. The lumen extends beyond the distal end of the endoscope and deflects at the distal end as desired by the operator's manipulation of a controller device. This distal end deflection may occur through various different techniques where the ability to deflect the lumen gives the operator increased control and maneuverability over the surgical implements located in the lumen. Depending upon the particular requirements of the surgical procedure, the controllable sheath may include any number of lumens capable of distal end deflection.