A surgical instrument comprising a handle assembly, an elongated portion, a head portion, an approximation mechanism, and a lockout mechanism is disclosed. The handle assembly comprises a movable handle and a stationary handle. The elongated portion extends distally from the handle assembly and defines a longitudinal axis. The head portion is disposed adjacent a distal portion of the elongated portion, and comprises a first jaw member and a second jaw member. The approximation mechanism comprises a drive member disposed in mechanical cooperation with the first jaw member and is configured to longitudinally move the first jaw member in relation to the second jaw member. The lockout mechanism is configured to selectively permit actuation of the movable handle to eject fasteners from the second jaw member. The lockout mechanism comprises a pin extending from the movable handle and is slidingly engaged with a slot in the drive member.
