Objective To measure the vertical height of mesio- distal marginal ridge to cusp in posterior teeth, which may be helpful to brackets positioning. Methods The study groups comprised of 60 patients（30 men, 30 women, mostly aged 12 - 14 years） who underwent orthodontic treatment without tooth extraction and matched the Andrews normal occlusion standard after treatment. Study model of each patient was made. Three- dimensional laser measurer was used to evaluate the vertical height of mesio- distal marginal ridge to mesial cusp in posterior teeth. The data were stored in a personal computer and submitted to statistical analysis of paired t test. Results No statistical significant difference was found in the same teeth between men and women. Not only in maxilla but also in mandible, there was no significant difference between the left and the right（P>0.05）. The average vertical height of maxillary first premolars was （1.70±0.50）mm, the maxillary second premolars was （1.24±0.45）mm, and for maxillary first molars, the result was （0.83±0.40）mm. The difference between each result was statistically significant（P
