Abstract: To investigate the role and clinical significance of cyclin G1 and PCNA in the pathogenesis of leiomyoma of the uterus. Methods: The expression levels of Cyclin G1 and PCNA in the 45 leiomyoma cases and peripheral normal myometrium were determined using the semi -quantitative reverse transcriptase polymerase chain reaction (RT - PCR) technique and through immunohistochemistry using the Streptavidin- Peroxidase (SP) method. Results: The expression of cyclin G1 and PCNA in leiomyoma was much higher than in myometrium. There was a significant difference between the two (P<0.05). There was a positive correlation between the expression levels of cyclin G1 and PCNA in leiomyoma, whereas no obvious correlation was found between the expression levels of cyclin G1 and PCNA in myometrium. Conclusion: Abnormal expression of Cyclin G1 may increase proliferation in the uterine leiomyoma cells through PCNA. The upregulated expression of cyclin G1 and PCNA closely correlates with the pathogenesis and development of uterine leiomyoma.