A surgical instrument (114, 164, 172, 200), comprising: a handle module (72) including at least one handle providing gripping surfaces for holding the instrument (114, 164, 172) by hand anda drive assembly (74) selectively removable from the handle assembly (72), the drive assembly including: an elongated shaft member (90, 122) defining a longitudinal axis an end effector (174) supported at a distal end of the elongated shaft member (90, 122), the end effector including a pair of opposed jaw members (140, 142, 180, 182) wherein at least one of the jaw members is movable relative to the elongated shaft member (90, 122) between open and closed positions with respect to the other jaw member a reciprocating drive member (92, 126) extending at least partially though the elongated shaft member (90, 122), the drive member (92) operably coupled to the end effector to induce movement of the jaw members (140, 142, 180, 182) between the open and closed positions in response to longitudinal reciprocation of the drive member (92, 126) a motor (86, 88, 116, 118) operable to move the reciprocating drive member (92, 126) longitudinally through the elongated shaft (90, 122) and a housing (110) substantially surrounding the motor (86, 88, 116, 118) and the reciprocating drive member (92, 126), the housing (110) substantially impervious to moisture and an actuator (102, 104) supported on the housing (110), the actuator operable to activate the motor (86, 88, 116, 118).
