A surgical fastener applying apparatus is provided including a cartridge half-section and an anvil half-section, the cartridge half-section and anvil half-section being relatively movable from an unclamped position to a clamped position; and a loading unit receivable in the cartridge half-section and having a plurality of staples and a plurality of staple pusher members. The cartridge half-section includes a frame; a member being longitudinally movable through the loading unit to interact with the plurality of staple pusher members to fire the staples; and a lockout mechanism arranged to block advancement of the member in a locked-out position of the lockout mechanism. In use, after loading of the loading unit in the surgical fastener applying apparatus and subsequent clamping of the cartridge and anvil half-sections, the lockout mechanism is moved to an unlocked position to allow advancement of the member.