Salivary glucose concentrations, following tasting of a 10 ml glucose solution, declined to sub-threshold levels sooner than the elicited persistence of sweetness response. Thus persistence cannot be explained by residual stimulus in the oral fluid. Panellists experience ‘saturation of sweetness intensity’ at lower concentrations of sugar than those which cause ‘saturation of persistence’, which suggests that separate mechanisms are responsible for the intensity and persistence effects. Increases of volume from 10 −2 ml to 1 ml of tasted solution, as well as increases of concentration, cause elevation of both intensity and persistence of sweetness although volume change does not affect intensity of response at low concentrations. These observations can be explained by assuming that the persistence of sweetness response is caused by localised concentrations of stimulus at or near the receptor while intensity is governed by the accessibility of receptors to stimuli at these sites.