Partitioning of hydrophobic cations, tetraphenylphosphonium (TPP+) and triphenylphosphonium homologues ((Phe)(3)-P+-(CH2)(n)CH3, n = 0-6), into lipid bilayers was studied by chromatography on immobilized small and large unilamellar liposomes (SUVs with mean diam of 30 nm and LUVs with 100 nm), The liposomes were immobilized stably in chromatographic gel beads by avidin-biotin (Yang et al, J. Chromatogr. B. 1998, 707, 131). By immobilized liposome chromatography (ILC), membrane partition coefficients (K-LM) Of the cations were measured. The K-LM values were coincident with molar partition coefficient, K-m, which was determined for some of cations by an ultrafiltration method. Temperature dependence of k(LM) Save the thermodynamic quantities of membrane partitioning, Delta H degrees (enthalpy change) and Delta S degrees (entropy change). The same quantities were also measured with isothermal titration calorimetry (ITC), and the values of both methods were similar to each other. This confirms the usefulness of ILC on the basis of its simplicity. Except for TPMP+ (n = 0), both Delta H degrees and Delta S degrees were positive, meaning that their membrane partitioning is entropy-driven. The values of both Delta H degrees and Delta S degrees did not depend on whether II was odd or even. Thus, the odd-even pattern of the activation energy for the planar lipid membrane transport of these phosphonium cations (Ono et al, Biochemistry 1994, 33, 4312-4318) originates from the odd-even pattern of the translocation process within the hydrophobic core of the bilayer membrane. The origin of the odd-even pattern was discussed.