Living things use solar energy in two ways: in the transmission of information and in the conversion of light energy to chemical energy. In order to elucidate the molecular mechanisms of highly sensitive visual responses and other photosensitive responses of biological systems, and the very efficient transduction of photoenergy to chemical energy in photosynthesis, it is important to observe molecular processes in biological systems. Using highly developed laser spectroscopic techniques, great progress has recently been achieved in the area of various primary processes in photobiology. It was therefore an excellent time to hold the 12th Taniguchi International Symposium, Biophysics Division, on Primary Processes in Photobiology. This volume is the proceedings of that symposium. Among the topics discussed are the femtosecond molecular processes in photosynthetic bacteriochlorophyll and the recently discovered intermediates in the photocycles of rhodopsin (found in the visual pigments of many animals), bacteriorhodopsin (found in the proton-pumping pigments of halobacteria) and retinochrome. New techniques for the measurement of the primary processes are also reported.