The small unilamellar vesicles (liposomes) of phospholipides, dimyristoylphosphatidylcholine (DMPC) and dicetyl phosphate (DCP), DMPC: DCP, incorporating a coumarin dye, 4-heptadecylumbelliferone, HUF, and all-trans retinal, RT, were prepared by sonication method. Because of the acid-base equilibrium, most of HUF molecules in the liposomes were either in the acidic form (pH 7.0) or in the basic form (pH 11.4) according as pH of the dispersion, which were distinguished by absorption and fluorescence spectra. Examination of absorption spectra, fluorescence emission and fluorescence excitation spectra ofliposome dispersions (pH 7.0) revealed that energy transfer from excited HUF molecule (donor) to RT molecule (acceptor) is possible, resulting in quenching of fluorescence of HUF. Along with fluorescence quenching, reduction of fluorescence lifetime of HUF in the basic form was observed. The dependence of fluorescence quenching efficiency and fluorescence lifetime on the density of RT at the liposome surface has been interpreted on the basis of two-dimensional FOrster mechanism. As retinal analogues are widely distributed in photoreceptors, excitation energy transfer to RT observed in this work would be significant for development of novel imaging materials, optical sensors and memory devices based on the retinal proteins such as bacteriorhodopsin and rhodopsin.