AN OBJECT OF THE PRESENT INVENTION IS TO PROVIDE A NUCLEIC ACID DELIVERY CARRIER COMPOSITION OF LOW TOXICITY AND HIGH SAFETY, THE CARRIER COMPOSITION, WHEN USED TO ADMINISTER A NUCLEIC ACID SUCH AS AN SIRNA INTO AN ANIMAL-DERIVED CELL OR ORGANISM, BEING CAPABLE OF DELIVERING EFFICIENTLY THE NUCLEIC ACIDS INTO THE CELLS WHILE PROTECTING IT FROM BEING DEGRADED； AND A NUCLEIC ACID DELIVER COMPOSITION CONTAINING THE CARRIER AND A NUCLEIC ACID. THE CARRIER COMPOSITION FOR DELIVERY OF A NUCLEIC ACID IS PREPARED BY MIXING (A) A CATIONIC LIPID HAVING A STEROID SKELETON WITH (B) A TERTIARY AMMONIUM SALT-TYPE CATIONIC LIPID. THE NUCLEIC ACID DELIVERY COMPOSITION IS PREPARED BY MIXING THE NUCLEIC ACID DELIVERY CARRIER WITH A NUCLEIC ACID.
