A composition for nucleic-acid introduction which is lowly cytotoxic and is improved in the intracellular introduction of a nucleic acid to be introd uced and in the intracellular expression thereof. The composition for the in tracellular introduction of a nucleic acid comprises a compound represented by the following formula (I) (wherein R1 and R2 are the same or different an d each means a C12-22 (un)saturated hydrocarbon group; R3 means C1-6 alkyl o r C1-6 hydroxyalkyl; m means an integer of 1-10; and X means halogeno) and a phospholipid. (I)
