An amphoteric liposome comprising: (a) neutral lipids selected from cholesterol or a mixture of cholesterol and at least one neutral or zwitterionic lipid, wherein κ(neutral) of said mixture is 0.25 or less and wherein κ(neutral) is calculated by the following formula: κ neutral = κ Lipid 1 ∗ c Lipid 1 + κ Lipid 2 ∗ c Lipid 2 + ... κ Lipid i ∗ c Lipid i wherein κ(Lipid) is the κ value of the appropriate neutral or zwitterionic lipid, c(Lipid) is the concentration of said lipid and i is the running variable, wherein κ is the volume ratio between the polar and apolar section of a lipid: κ = molecular volume head / molecular volume tail ; wherein the mixture of cholesterol and at least one neutral or zwitterionic lipid is selected from the group consisting of: (i) cholesterol/phosphatidylcholine; (ii) cholesterol/phosphatidylethanolamine; and (iii) cholesterol/phosphatidylethanolamine/phosphatidylcholine; and (b) a mixture of lipid components comprising: (i) a stable cationic lipid and a chargeable anionic lipid, referred to as amphoter I mixture; or (ii) a chargeable cationic lipid and a chargeable anionic lipid, referred to as amphoter II mixture; or (iii) a chargeable cationic lipid and a stable anionic lipid, referred to as amphoter III mixture; further wherein the mixture of lipid components comprises at least one lipid ion which is a pH-sensitive, weak acid or base which is chargeable; and further wherein the minimum value of κ(total) of the mixture is smaller than 0.25. (a) neutral lipids selected from cholesterol or a mixture of cholesterol and at least one neutral or zwitterionic lipid, wherein κ(neutral) of said mixture is 0.25 or less and wherein κ(neutral) is calculated by the following formula: κ neutral = κ Lipid 1 ∗ c Lipid 1 + κ Lipid 2 ∗ c Lipid 2 + ... κ Lipid i ∗ c Lipid i wherein κ(Lipid) is the κ value of the appropriate neutral or zwitterionic lipid, c(Lipid) is the concentration of said lipid and i is the running variable, wherein κ is the volume ratio between the polar and apolar section of a lipid: κ = molecular volume head / molecular volume tail ; wherein the mixture of cholesterol and at least one neutral or zwitterionic lipid is selected from the group consisting of: (i) cholesterol/phosphatidylcholine; (ii) cholesterol/phosphatidylethanolamine; and (iii) cholesterol/phosphatidylethanolamine/phosphatidylcholine; and wherein κ(Lipid) is the κ value of the appropriate neutral or zwitterionic lipid, c(Lipid) is the concentration of said lipid and i is the running variable, wherein κ is the volume ratio between the polar and apolar section of a lipid: κ = molecular volume head / molecular volume tail ; wherein the mixture of cholesterol and at least one neutral or zwitterionic lipid is selected from the group consisting of: (i) cholesterol/phosphatidylcholine; (ii) cholesterol/phosphatidylethanolamine; and (iii) cholesterol/phosphatidylethanolamine/phosphatidylcholine; and (i) cholesterol/phosphatidylcholine; (ii) cholesterol/phosphatidylethanolamine; and (iii) cholesterol/phosphatidylethanolamine/phosphatidylcholine; and (b) a mixture of lipid components comprising: (i) a stable cationic lipid and a chargeable anionic lipid, referred to as amphoter I mixture; or (ii) a chargeable cationic lipid and a chargeable anionic lipid, referred to as amphoter II mixture; or (iii) a chargeable cationic lipid and a stable anionic lipid, referred to as amphoter III mixture; (i) a stable cationic lipid and a chargeable anionic lipid, referred to as amphoter I mixture; or (ii) a chargeable cationic lipid and a chargeable anionic lipid, referred to as amphoter II mixture; or (iii) a chargeable cationic lipid and a stable anionic lipid, referred to as amphoter III mixture; <EOS>