【Objective】To observe the effect of plasma ?-endogenous peptides (?-EP) on gestational function in endometriosis(EMT) rats.【Methods】 Female SD rats at the third estrous cycle were used to establish EMT model.Then 20 EMT rats were equally randomized into the model group and naltrexone(an opioid receptor antagonist) group,and other 10 rats were in the pseudo-operation group.Naltrexone group was given naltrexone 2?mg?kg~-1?d~-1 by gastric gavage during proestrus and normal saline at other time,and the model group and pseudo-operation group were given normal saline for one month.Serum levels of ?-EP,luteinizing hormone(LH) and prolactin(PRL) were examined during proestrus,and serum progesterone(P) level and gestational function were observed after estrus.【Results】Serum levels of ?-EP and PRL increased and LH decreased during proestrus,and serum P level also decreased after estrus in the model group(P