Elastic band ligation device for treating hemorrhoidal tissue, including an inner tube for retaining an elastic band, a plunger in the inner tube for drawing hemorrhoidal tissue into the inner tube, and an outer tube pusher sleeve disposed over the inner tube. A thumb pusher on the sleeve allows the operator to push the sleeve towards the front of the inner tube to deploy the elastic band from the front end of the inner tube onto hemorrhoidal tissue drawn into the inner tube. The sleeve has a locking mechanism including a tab for locking the sleeve to the inner tube to prevent relative movement of the sleeve and inner tube until the sleeve is unlocked by the user, thereby preventing premature deployment of an elastic band.
