An adapter assembly for selectively interconnecting a surgical loading unit that is configured to perform a function and a surgical device that is configured to actuate the surgical loading unit, the surgical loading unit including an axially translatable drive member (338b, 338c), and the surgical device including a plurality of rotatable drive shafts, the adapter assembly comprising: a housing configured and adapted for connection with the surgical device; an outer tube extending distally from the housing to a distal end portion configured and adapted for connection with the surgical loading unit; and a firing assembly supported within the housing and the outer tube, the firing assembly including: a firing shaft including a proximal end configured for operative engagement with a rotatable drive shaft of the plurality of rotatable drive shafts of the surgical device; a bevel gear assembly including a proximal end in mechanical engagement with a distal end portion of the firing shaft; a ring gear disposed within the distal end portion of the outer tube; a sun gear disposed at a distal end of the bevel gear assembly within the ring gear; a plurality of planetary gears disposed around and meshingly engaged with teeth of the sun gear and teeth of the ring gear; a plate operably coupled to the plurality of planetary gears; and a distal gear disposed on a shaft extending distally from the plate, the distal gear being operatively engageable with the axially translatable drive member of the surgical loading unit; characterised in that the firing assembly further includes a spider gear operably coupled to the plate and disposed proximal of the ring gear, and wherein the distal end portion of the outer tube includes a switch having a tab extending distally from a distal end of the switch and an extension extending inwardly toward a center of the outer tube, the switch being movable between a proximal position in which the tab is disengaged from the ring gear and the extension is engaged with the spider gear such that the plate is held stationary to allow the plurality of planetary gears to rotate the distal end portion of the outer tube, and a distal position in which the tab is engaged with the ring gear and the extension is disengaged from the spider gear such that the ring gear is held stationary to allow the plurality of planetary gears to effect a function of the surgical loading unit. a housing configured and adapted for connection with the surgical device; an outer tube extending distally from the housing to a distal end portion configured and adapted for connection with the surgical loading unit; and a firing assembly supported within the housing and the outer tube, the firing assembly including: a firing shaft including a proximal end configured for operative engagement with a rotatable drive shaft of the plurality of rotatable drive shafts of the surgical device; a bevel gear assembly including a proximal end in mechanical engagement with a distal end portion of the firing shaft; a ring gear disposed within the distal end portion of the outer tube; a sun gear disposed at a distal end of the bevel gear assembly within the ring gear; a plurality of planetary gears disposed around and meshingly engaged with teeth of the sun gear and teeth of the ring gear; a plate operably coupled to the plurality of planetary gears; and a distal gear disposed on a shaft extending distally from the plate, the distal gear being operatively engageable with the axially translatable drive member of the surgical loading unit; a firing shaft including a proximal end configured for operative engagement with a rotatable drive shaft of the plurality of rotatable drive shafts of the surgical device; a bevel gear assembly including a proximal end in mechanical engagement with a distal end portion of the firing shaft; a ring gear disposed within the distal end portion of the outer tube; a sun gear disposed at a distal end of the bevel gear assembly within the ring gear; a plurality of planetary gears disposed around and meshingly engaged with teeth of the sun gear and teeth of the ring gear; a plate operably coupled to the plurality of planetary gears; and a distal gear disposed on a shaft extending distally from the plate, the distal gear being operatively engageable with the axially translatable drive member of the surgical loading unit; characterised in that the firing assembly further includes a spider gear operably coupled to the plate and disposed proximal of the ring gear, and wherein the distal end portion of the outer tube includes a switch having a tab extending distally from a distal end of the switch and an extension extending inwardly toward a center of the outer tube, the switch being movable between a proximal position in which the tab is disengaged from the ring gear and the extension is engaged with the spider gear such that the plate is held stationary to allow the plurality of planetary gears to rotate the distal end portion of the outer tube, and a distal position in which the tab is engaged with the ring gear and the extension is disengaged from the spider gear such that the ring gear is held stationary to allow the plurality of planetary gears to effect a function of the surgical loading unit.