To study the chin morphology of Cantonese with normal occlusion, and to establish the cepha-lometric database of the chin morphology for providing reference data for clinical orthodontic treatment and surgical treatment of Chin.

The lateral cephalometrics radiographs of 44 untreated samples (20 men, 24 women) were taken in natural head position, centric oclusion and lip relaxed position. The chin characteristic variables were measured by Winceph 7.0 software three times by one orthodontists. Mean and standard deviations of measurements were determined for each gender. The t-test was used to compare the values between males and females.

The obtained data were statistically analyzed and compared between male and female. There are sex difference in M-Me to MP/ B-Me to MP and B′ to Li-Pog′ (mm). There is no sex difference in Chin curvature.

The normative data for the Southern Chinese should be uesd as a guide for diagnosis and treatment of chin deformities. The maxillofacial surgeon and orthodontist should consider the sex difference. Gender differences must be taken into consideration during orthodontic diagnosis and treatment planning for the individual patient.