Despite the existence of a continually expanding literature on gustation, the psychophysical constants for the sensory scale of perceived liquid volume held in the mouth have not previously been reported. Neither the Weber fraction for the effective discriminability of water volume differences nor the psychophysical power function relating perceived to actual volume (or weight) have been investigated. It is to remedy this omission that the present study is undertaken. In addition, an attempt is here made to elucidate the extent and importance of suspected individual differences in judgements (due to sex and due to anxiety about choking or swallowing when large liquid volumes are retained in the mouth) such as have previously been observed in gustatory comparison experiences.