The lip-shape recognition of Japanese vowels utilizing a stereoscopic vision system has been performed to enhance the discrimination of five vowels by machine lip-reading. The opening angle P4 between the upper lip and the lower lip is selected as the typical three-dimensional feature parameter of lip shape, in addition to the usual feature parameters such as the width P1 and the height P2 of the lip shape and distance P3 between the tips of the upper lip and the chin. Compared with the 3 two-dimensional parameters P1, P2 and P3 used in a single-vision system, the 3 and 4 three-dimensional parameters led to the significant increase of discrimination rate, and in particular, the discrimination rate by the 4 three-dimensional parameters was more than 90% for every tested subject. Recognition for an unspecified subject was also examined, based on the selections of the variance-covariance matrix and the mean vector of feature variables, by which the Mahalanobis' generalized square distance and the maximum likelihood discrimination function were determined.