The hypothesis was offered some years ago (Greenwood, 1961) that critical bandwidth in man was an exponential function of distance on the basilar membrane. Integration of the function yielded directly a frequency-position curve fitting Békésy's data. Thus critical bandwidth in man was apparently proportional, and if distance was scaled in millimeters, numerically equal, to the derivative of the frequency-position function. It was unlikely, however, that critical bandwidth would correspond to the same distance in species with cochleas of different sizes. Scale relations between frequency-position functions of a few species, and between displacement envelopes in four species (Greenwood, 1962), suggested that critical bandwidth might correspond to scale-related distances, implying changes among species in the constant of proportionality to the derivative of the frequency-position function. Based on a 1-mm distance in man, some unpublished calculations of scaled distances were made for other species. Subsequently, a revised CB function was suggested for man (Greenwood, 1971) in which critical bandwidth corresponds to 1.25 mm. Based on this distance, scale-related functions are suggested for cat, squirrel monkey, and guinea pig in which critical bandwidth corresponds, respectively, to distances of about 0.78, 0.71 +, and 0.61 mm. These values may be related to distance measures derived from physical and physiological data in those species.