Abstract: The invention relates to a surgical stapler for applying at least two rows of staples, said surgical stapler comprising a cartridge housing said rows of staples and having a slot extending along the cartridge between two rows of staples, said surgical stapler further comprising a cutting means movable along said slot and a lockout mechanism for preventing movement of said cutting means, wherein said lockout mechanism comprises a blocking member movable between a first position, in which the blocking member blocks movement of said cutting means, and a second position, in which the blocking member permits movement of said cutting means, and a biasing member for biasing said blocking member towards said first position and wherein said cartridge comprises a release member for moving said blocking member towards said second position upon insertion of said cartridge into said surgical stapler.