A surgical stapling apparatus comprising: a body portion defining a longitudinal axis having a proximal end and a distal end; a tool assembly supported on the distal end of the body portion, the tool assembly including an anvil assembly and a cartridge assembly having a cartridge body defining a distal and a proximal end, the tool assembly being movable from an unapproximated position to an approximated position, a drive member movably supported within the tool assembly from a retracted position to an advanced position to move the tool assembly from the unapproximated position to the approximated position, the drive member having a base and a stop surface distal to said base; a firing lockout assembly including a latch member having a blocking member and a biasing member, the latch member being pivotally supported within the tool assembly and movable from a first position to a second position, wherein in the first position the blocking member of the latch member is aligned with the stop surface of the drive member to prevent advancement of the drive member within the tool assembly and in the second position the blocking member is misaligned with the stop surface of the drive member to permit advancement of the drive member within the tool assembly, the biasing member being positioned to urge the latch member towards the first position; and an actuation sled positioned within the tool assembly to be engaged by the drive member as the drive member is moved from the retracted position towards the advanced position, the drive member effecting movement of the actuation sled from a retracted position to an advanced position upon movement of the drive member from the retracted position to the advanced position, characterized in that the actuation sled is configured to engage the latch member to move the latch member from the first position to the second position when the actuation sled is advanced distally within the cartridge assembly by the drive member to allow the base of the drive member to pass over the stop surface such that said base retains the latch member in the second position; wherein the surgical stapling apparatus is further configured such that when it has been fired and the drive member is being returned to the retracted position, the actuation sled remains in the distal end of the cartridge body and when it is returned to the retracted position the latch member moves to the first position to prevent readvancement of the drive member. a body portion defining a longitudinal axis having a proximal end and a distal end; a tool assembly supported on the distal end of the body portion, the tool assembly including an anvil assembly and a cartridge assembly having a cartridge body defining a distal and a proximal end, the tool assembly being movable from an unapproximated position to an approximated position, a drive member movably supported within the tool assembly from a retracted position to an advanced position to move the tool assembly from the unapproximated position to the approximated position, the drive member having a base and a stop surface distal to said base; a firing lockout assembly including a latch member having a blocking member and a biasing member, the latch member being pivotally supported within the tool assembly and movable from a first position to a second position, wherein in the first position the blocking member of the latch member is aligned with the stop surface of the drive member to prevent advancement of the drive member within the tool assembly and in the second position the blocking member is misaligned with the stop surface of the drive member to permit advancement of the drive member within the tool assembly, the biasing member being positioned to urge the latch member towards the first position; and an actuation sled positioned within the tool assembly to be engaged by the drive member as the drive member is moved from the retracted position towards the advanced position, the drive member effecting movement of the actuation sled from a retracted position to an advanced position upon movement of the drive member from the retracted position to the advanced position, characterized in that the actuation sled is configured to engage the latch member to move the latch member from the first position to the second position when the actuation sled is advanced distally within the cartridge assembly by the drive member to allow the base of the drive member to pass over the stop surface such that said base retains the latch member in the second position;