Abstract： Objective To investigate the influence of di-(2-ethylexyl) phthalate (DEHP) on cell apoptosis and expression of Bcl-2 and bax in cultured human first trimester cytotrophoblasts. Methods Human first trimester cytotrophoblasts were cultured with DEHP at concentration of 0, 25, 50, 100 μmol/Lfor 24 hours. Cell apoptosis was detected by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) and flow cytometer method. The expression of apoptosis-associated genes, including Bcl-2 and bax, were detected by reverse transcription (RT)-PCR in cultured cytotrophoblast cells. The protein expression of Bcl-2 and bax in cytotrophoblast cells was measured by western blot. Results (1) The expression of Bcl-2: when incubated with DEHP at concentration of 0, 25,50 and 100 μmol/L, the expression of Bcl-2 were 1.00 ± 0.05, 1.03 ± 0.04, 1.04 ± 0.03, 1.04± 0.04,which did not show statistical difference ( P > 0.05 ). The expression of Bcl-2 protein were 0.11 ± 0.02,0.11 ±0.04, 0.12±0.02, 0.12 ±0.03, which also didn't reach statistical difference (P>0.05). (2)The expression of bax: when incubated with DEHP at concentration of 50 and 100 μmol/L, the expression of bax protein were 0.63 ± 0.04 and 0.81 ± 0.04, which were significantly higher than 0.23 ± 0.05 with DEHP at 0 μmol/L (P < 0.05). The expression of bax mRNA were 0.96 ± 0.04 and 1.02 ± 0.04, which was significantly higher than 0.81 ±0.05 with DEHP at 0 μmol/L (P < 0.05). (3) Apoptosis: when incubated with DEHP at concentration of 50 and 100 μmol/L for 24 hours, the apoptotic cell ratio were ( 18.8 ± 2.6) % and ( 20.3 ± 2.0) % by annexin V-FITC/PI staining, which were significantly higher than (10.6±1.4)% at 0 μmol/L and (18.1 ±4.6)% and (19.5 ±1.2)% by TUNEL staining, which were significantly higher than ( 11.2 ± 3.1 ) % at 0 μmol/L of DEHP (P < 0.05). Conclusion DEHP could induce apoptosis of cytotrophoblast cells by increasing bax gene expression, but had no effect on Bcl-2 expression.