A surgical stapling device comprising: an elongate body having a proximal portion and a distal portion; a tool assembly supported on the distal portion of the elongate body, the tool assembly including: a cartridge assembly including a channel member and a staple cartridge, the staple cartridge removably received within the channel member and including a cartridge body, staples, and an actuation sled assembly including an actuation sled, the actuation sled assembly movable through the cartridge body between retracted and advanced positions; an anvil including an anvil body that is coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions; and a lock mechanism supported on the anvil, the lock mechanism including a lock member that is rotatable between a locked position and an unlocked position in response to movement of the tool assembly from the open position to the clamped position; and a drive assembly including a clamp member, the clamp member movable in relation to the tool assembly between retracted and advanced positions, wherein the lock member is positioned to prevent movement of the clamp member from the retracted position to the advanced position in the locked position when the tool assembly is in the clamped position, wherein the lock member is biased towards the locked position wherein the lock mechanism includes a biasing member to urge the lock member towards the locked position, characterised in that the biasing member includes a coil spring; and in that the actuation sled assembly includes a knife that is supported on the actuation sled; wherein the lock member engages the knife of the actuation sled assembly when the actuation sled assembly is in its retracted position to retain the lock member in the unlocked position. an elongate body having a proximal portion and a distal portion; a tool assembly supported on the distal portion of the elongate body, the tool assembly including: a cartridge assembly including a channel member and a staple cartridge, the staple cartridge removably received within the channel member and including a cartridge body, staples, and an actuation sled assembly including an actuation sled, the actuation sled assembly movable through the cartridge body between retracted and advanced positions; an anvil including an anvil body that is coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions; and a lock mechanism supported on the anvil, the lock mechanism including a lock member that is rotatable between a locked position and an unlocked position in response to movement of the tool assembly from the open position to the clamped position; and a drive assembly including a clamp member, the clamp member movable in relation to the tool assembly between retracted and advanced positions, wherein the lock member is positioned to prevent movement of the clamp member from the retracted position to the advanced position in the locked position when the tool assembly is in the clamped position, wherein the lock member is biased towards the locked position wherein the lock mechanism includes a biasing member to urge the lock member towards the locked position, a cartridge assembly including a channel member and a staple cartridge, the staple cartridge removably received within the channel member and including a cartridge body, staples, and an actuation sled assembly including an actuation sled, the actuation sled assembly movable through the cartridge body between retracted and advanced positions; an anvil including an anvil body that is coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions; and a lock mechanism supported on the anvil, the lock mechanism including a lock member that is rotatable between a locked position and an unlocked position in response to movement of the tool assembly from the open position to the clamped position; and a drive assembly including a clamp member, the clamp member movable in relation to the tool assembly between retracted and advanced positions, wherein the lock member is positioned to prevent movement of the clamp member from the retracted position to the advanced position in the locked position when the tool assembly is in the clamped position, wherein the lock member is biased towards the locked position wherein the lock mechanism includes a biasing member to urge the lock member towards the locked position, characterised in that the biasing member includes a coil spring; and in that the actuation sled assembly includes a knife that is supported on the actuation sled; wherein the lock member engages the knife of the actuation sled assembly when the actuation sled assembly is in its retracted position to retain the lock member in the unlocked position.