A surgical stapler for stapling tissue, comprising: a curved end effector, comprising: a staple cartridge configured to removably store staples therein, said staple cartridge having a first surface defined by a first radius of curvature and having a curved slot; a channel configured to receive the staple cartridge; an anvil configured to deform said staples, said anvil having a second surface defined by a second radius of curvature, wherein said first and second surfaces are configured to releasably hold said tissue between said first surface and said second surface when said first surface and said second surface are placed in close opposition to each other; a cutting member having a cutting edge, wherein said cutting member is received and guided by the curved slot, and is relatively movable with respect to said anvil and the staple cartridge; and a flexible driver operably engaged with said cutting member to advance said cutting member through the curved slot, wherein said driver has a width and a height, perpendicular to said width, wherein said width is greater than said height, such that the driver is more flexible with respect to its height, i.e. in an upward and downward direction, than with respect to its width, and the surgical stapler being characterised in that: said width extends in a direction that is perpendicular to a plane in which said cutting edge moves, and the end effector and slot are curved in the downward or upward direction, in a plane that is substantially parallel to the plane in which said cutting edge moves. a curved end effector, comprising: a staple cartridge configured to removably store staples therein, said staple cartridge having a first surface defined by a first radius of curvature and having a curved slot; a channel configured to receive the staple cartridge; an anvil configured to deform said staples, said anvil having a second surface defined by a second radius of curvature, wherein said first and second surfaces are configured to releasably hold said tissue between said first surface and said second surface when said first surface and said second surface are placed in close opposition to each other; a staple cartridge configured to removably store staples therein, said staple cartridge having a first surface defined by a first radius of curvature and having a curved slot; a channel configured to receive the staple cartridge; an anvil configured to deform said staples, said anvil having a second surface defined by a second radius of curvature, wherein said first and second surfaces are configured to releasably hold said tissue between said first surface and said second surface when said first surface and said second surface are placed in close opposition to each other; a cutting member having a cutting edge, wherein said cutting member is received and guided by the curved slot, and is relatively movable with respect to said anvil and the staple cartridge; and a flexible driver operably engaged with said cutting member to advance said cutting member through the curved slot, wherein said driver has a width and a height, perpendicular to said width, wherein said width is greater than said height, such that the driver is more flexible with respect to its height, i.e. in an upward and downward direction, than with respect to its width, and the surgical stapler being characterised in that: said width extends in a direction that is perpendicular to a plane in which said cutting edge moves, and the end effector and slot are curved in the downward or upward direction, in a plane that is substantially parallel to the plane in which said cutting edge moves. said width extends in a direction that is perpendicular to a plane in which said cutting edge moves, and the end effector and slot are curved in the downward or upward direction, in a plane that is substantially parallel to the plane in which said cutting edge moves.