This chapter provides an overview of memory psychophysics. Psychophysics is the science that explicates the functional relations between physical stimuli and the resulting sensory responses. Memory psychophysics, or mnemophysics, is the branch of psychophysics that treats the functional relations between physical stimuli and their remembered sensory responses. Memory psychophysics derives from the two branches of experimental psychology. Both psychophysicists and memory researchers are interested in the quantitative measurement of the correspondence between the objective properties of the stimulus and their subjective counterparts in the human cognitive system. The study of memory and psychophysics has developed independently, using separate methods of experimentation and analysis. The chapter presents the main hypotheses that have been suggested to account for the rather small body of empirical findings.