Abstract: Objective To study the impacts of di-(2-ethylhexyl) phthalate(DEHP) on expressions of hormone including estradiol (E₂) and progesterone (P₄),and follicle development in ovary of immature mice.Methods Sixty ICR female mice were randomly divided into 4 groups:a negative control,three experimental groups treated with DEHP at doses of 100,400, and 1 600 mg/kg,though stomach gavage onceA day and 5 days a week for 6 consecutive weeks. After the treatment, the mice's ovaries were prepared to detect te developments of follicles.Sera of the m ice were sampled to measure the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), E₂ and P₄.Results FSH level (0.72±0.04 mIU/ml) in high dosage group was higher then that of the control group (0.58±0.30 mIU/ml) (P<0.05).E₂ levels in low and medium dose groups (1.62±0.18 and 1.69±0.16 pg/mL) were significantly lower,but significantly higher in high dose DEHP group than that of the control group (P<0.05 for all).Conclusion DEHP has obvious development toxicity to ovary of immature female mice.