A surgical stapling device includes a tool assembly including an anvil and a cartridge assembly that are movable in relation to each other between open and clamped positions. The cartridge assembly includes a staple cartridge that can be replaced after each firing of the stapling device to facilitate reuse of the stapling device. The anvil includes a lockout mechanism that prevents operation of the stapling device when the staple cartridge has been previously fired. The lockout mechanism is adapted to move from a locked position to an unlocked position when the staple cartridge is replaced and the tool assembly is moved from the open position to the clamped position.