Abstract: Objective: To detect the expression of Wnt5a mRNA in lesions of chronic apical periodontitis. Methods: 18 patients of chronic apical periodontitis were divided into group A (d≥6 mm) and group B (6 mm＞d≥3 mm) according to the scope of the root lesions. 21 healthy teeth extracted for orthodontic reasons were selected as the control group. Expression of Wnt5a mRNA was analyzed with RT-PCR (Real-Time PCR) to identify its relationship with the scope of the lesion. 10 patients of chronic apical periodontitis and 5 healthy controls were chosen for immunohistochemistry. All statistical analysis was performed using the SPSS 13.0 statistical package. Results: Wnt5a mRNA expression in patients increased significantly than that in normal controls (P<0.05). Compared with control group, group A had a significant increase in Wnt5a mRNA expression (P<0.01). The difference between group A and group B was also significant (P<0.01). While there was no significant difference between group B and the control group (P＞0.05). According to the results of immunohistochemistry, Wnt5a expression in group A (P＜0.01) and group B (P＜0.05) was significantly higher than that in normal controls. Wnt5a expression in group A was higher than that in group B (P＜0.05). Conclusion: Wnt5a expression is associated with the bone resorption in chronic apical periodontitis.