Objective To observe the effect of Ciclosporin（CsP） on apoptosis and expression of the associated protein Bcl-2, Caspase-3 in gingival epithelium of rats in order to approach the mechanism of CsP-induced gingival epithelium overgrowth. Methods Eighty SPF grade male 7-week-old Wistar rats were randomly divided into experimental group and control group, and each group was divided into 4 subgroups according to the duration of treatment（10, 20, 30 and 40 days）. The experimental objects were given fresh milk including CsP intragastrically and the control ones were given only fresh milk. After perfusion of 4% paraform for internal fixation, the specimens’bucco-lingual paraffin sections at lower first molar were made. Apoptosis was detected using TdT-mediated dUT nick end labeling（TUNEL） and the expression of Bcl-2 and Caspase-3 using immunohistochemisty of PV. The apoptotic index, positive cell rate of Caspase-3 and average gray scale of Bcl-2 was measured with an image analysis system. Data were analyzed by two-way analysis of variance of factorial design. Results The apoptosis index and positive cell rate of Caspase-3 were downregulated in the experimental group, and were significant difference from the control group（P
