Abstract: Objective: To explore the relationship between the testosterone（T） levels in serum and follicular fluid and the outcomes of stimulation in vitro fertilization-embryo transfer（IVF-ET） cycle. Methods: Data was collected from 43 patients who received IVF/ intracytoplasmic sperm injection（ICSI） treatment between May and August in 2011 at our center. T levels in serum and follicular fluid were detected by chemiluminiscence ELISA. ①43 patients were divided into 3 groups by the number of harvested oocytes: group L（1-5 oocytes）, group M （6-15 oocytes） and group H （＞15 oocytes）. T levels, the fertilization rate and the clinical pregnancy rate were compared among three groups. ②43 patients were divided into the pregnant group and the non-pregnant group. T levels were then compared. Results: ①There were not significant differences in the follicular fluid T levels and the basal serum T level among three groups（P＞0.05）. There were significant differences in the serum T levels on the day of hCG administration among three groups（P＜0.05）. T level on the day of hCG administration in the H group was significantly higher than that in the M group（P=0.010） and the L group（P=0.001）. However, there were not significant differences in the serum T levels at other time points of COH among three groups（P＞0.05）. ②There were not significant differences in the fertilization rate and the rate of high quality embryo among three groups （P＞0.05）, however there was significant difference in the clinical pregnancy rate （P＜0.05）. ③The serum T level on the day of ovum pick-up in the pregnant group was significantly higher than that in the non-pregnant group （P＜0.05）; however there was not significant difference in the T level of follicular fluid（P＞0.05）. Conclusions: During the IVF-ET treatment, the basal level of serum T can not predict ovarian response and pregnancy outcome; however the T level on the day of hCG administration could be a parameter，to predict ovarian response. The serum T level on the day of ovum pick-up is associated with pregnancy outcome; however, the T in the follicular fluid is not associated with pregnancy outcome.

Key words: Fertilization in vitro, Embryo transfer, Testosterone, Superovulation, Pregnancy outcome, Follicular fluid