Objective: Using cone beam CT to investigate the root-canals of the mandibular first premolars and their morphological characteristics in Luzhou areas. Methods: Cone beam CT images of 872 cases mandibular first premolars were collected and numbered. The root-canal classification and bilateral symmetry were analyzed. Results: According to Vertucci classification,the incidence of type I canal configuration of mandibular first premolars was 85. 67%,type Ⅲ 3. 10%,type Ⅳ 0. 03%,type Ⅴ 8. 00% and C-shaped2. 87%. ...