Objective To study the characteristics of oral lips of the normal adults. Methods The oral lips of 556 college students, who are Han people of Hunan, were measured by digital sliding caliper. Results Eleven items had been measured, the length of upper lips = 0.726 × The length of lower lips + 0. 204, the width of philtrum = 0.163 × the width of mouth + 0.006, the medial crest of labial arch = 0.038 × the lateral crest of labial arch + 0. 652, the depth of upper vestibular groove = 0. 322 × the depth of lower vestibular groove + 7.3 l 1,...