Maximum biting force and chewing performance were measured in adult subjects before and after four-weeks training by newly devised "Chewing Ability Enhancing Substances (CAES)". The CAES is made of glucomannan. The number of chewing strokes and chewing time until the last swallowing action are much larger when chewing CAES than those of other usual eating materials. By four weeks training using CAES, the maximum biting force and chewing performance of the subject were clearly increased. However, this increased chewing ability began to return to the control level gradually 2 weeks after the cessation of the training.