We describe automatic visual speech segmentation using facial data captured by a stereo-vision technique. The segmentation is performed using an HMM-based forced alignment mechanism widely used in automatic speech recognition. The idea is based on the assumption that using visual speech data alone for the training might capture the uniqueness in the facial compo- nent of speech articulation, asynchrony (time lags) in visual and acoustic speech segments and significant coarticulation effects. This should provide valuable information that helps to show the extent to which a phoneme may affect surrounding phonemes visually. This should provide information valuable in labeling the visual speech segments based on dominant coarticulatory contexts.