BACKGROUND:: Age and dental age are shown to have some limitations in predicting skeletal maturity. OBJECTIVE:: To compare the mandibular length in boys and girls with Class I and Class II skeletal patterns by using the cervical vertebrae maturation, and to provide valid reference index for orthodontical treatment. METHODS:: The lateral cephalograms of the 160 cases of Class I (40 males and 40 females) and Class II (40 males and 40 females) skeletal patterns, aged 8-15 years, were taken before orthodontic treatment. The sample was grouped according to stages of the cervical vertebrae maturation (Hasse and Farman method), and the mandibular length was measured separately. The results were statistically analyzed by the independent-sample t test. RESULTS AND CONCLUSION:: No matter you are a male or female, the mandibular length of Class I was greater than that of Class II at the early stages of growth and development. In the Class I pattern, the mandibular lengths of boys were greater than those of girls at accelerated, transition, and deceleration stages (P < 0.05), whereas in the Class II pattern, the mandibular lengths of boys were greater than those of girls at accelerated, transition, and deceleration stages (P < 0.05). The present results indicate a sexual dimorphism in the mandibular length at almost all stages of bone maturation, but the possibility of a later “catch up” growth period occurs on Class II girls. And this information has important orthodontic clinical implications.Yang C, Zu Q, Leng CT, Gulibaha•Maimaitili. Comparison of mandibular length in patients with Class I and Class II skeletal patterns using the cervical vertebrae maturation. Zhongguo Zuzhi Gongcheng Yanjiu. 2014;18(2):187-192.