The aim of the 5th International Conference on Retinal Proteins was to present the latest findings of the interdisciplinary fields where photochemical, biophysical, molecular biology and physiological aspects are intimately linked. This symposium gathered some of the best scientists in the world to discuss two specific aspects: the common features and general functions of retinal proteins: Bacteriorhodopsin, Halorhodopsin, sensory and visual Rhodopsins and Retinochromes; the molecular processes intervening between absorption of the photon by the retinal proteins and the ensuing biological responses. These proceedings cover nearly all the presentations given during this symposium.