A pneumatically operated veterinary medicinal pellet implanter utilizes pressurized air to drive an impeller for dispensing medicinal pellets through a needle on an end of the implanter and into a cavity created by the needle under the skin of an animal to be treated. The pressurized air source may also be utilized to retract the impeller after dispensing of the pellets. The impeller is part of a piston slidingly secured within a pneumatic cylinder. Pressurized air is selectively and alternatingly supplied to the front and rear and rear of the cylinder for advancing the impeller between retracted and extended positions respectively. The pressure of the air supplied to the rear of the cylinder for driving the impeller is reduced relative to the pressure of the air supplied to the front of the cylinder for retracting the impeller.