The present invention provides pH-responsive liposomes which are capable of holding a desired substance in an acidic pH environment and releasing the desired substance in a basic pH environment.The present invention uses pH-responsive liposomes comprising, as constituent lipids thereof, a cationic amphiphilic molecule and at least one of an anionic amphiphilic molecule and a twitterionic amphiphilic molecule, wherein the liposomes, when dispersed in an aqueous medium, have a positive zeta potential in an acidic environment where the dispersion has a pH of less than 6.5 and have a negative zeta potential in a basic environment where the dispersion has a pH of 8.5 or more.
