AIM: To investigate the effect of norcantharidin on proliferation and invasion of human gallbladder carcinoma GBC-SD cells in vitro and its anticancer mechanism.METHODS: Human gallbladder carcinoma GBC-SD cells were cultured by cell culture technique. The growth and the invasiveness of GBC-SD cells in vitro were evaluated by the tetrazolium-based colorimetric assay and by the Matrigel experiment and the crossing-river test.Expression of PCNA, Ki-67, MMP2 and TIMP2 proteins of GBC-SD cells was determined by streptavidin-biotin complex method.RESULTS: In vitro norcantharidin inhibited the growth and proliferation of GBC-SD cells in a dose- and time-dependent manner, with the IC50 value of 56.18 μg/mL at 48 h.Norcantharidin began to inhibit the invasion of GBC-SD cells at the concentration of 5 μg/mL, and the invasive action of GBC-SD cells was inhibited completely and their crossing-river time was prolonged significantly at 40 μg/mL.After treatment with norcantharidin, the expression of PCNA, Ki-67, and MMP2 was significantly decreased. With the increase in TIMP2 expression, the MMP2 to TIMP2 ratio was decreased significantly (P＜0.05).CONCLUSION: Norcantharidin inhibits the proliferation and growth of human gallbladder carcinoma cells in vitro at relatively low concentrations by inhibiting PCNA and Ki-67expression. Its anti-invasive activity may be the result of decrease in MMP2 to TIMP2 ratio and reduced cell motility.