Abstract: Objective To investigate the variance of peripheral blood prolactin(PRL)in controlled ovarian stimulation.Methods Seventy-two patients,with totally 106 cycles receiving a long protocol of gonadotropin-releasing hormone agonist combined with gonadotropin(Gn)were randomly enrolled in this retrospective study.During controlled ovarian stimulation,peripheral blood hormones were measured by chemiluminescent microparticle immunoassay.Results Prolactin was positively correlated with estradiol (r=0.5897.P<0.01)while there was no significant correlation between luteinizing hormone and PRLProgesterone had a positive relation with prolactin(r=0.1412,P<0.01).Conclusions During controlled ovarian stimulation,prolactin secretion is not affected by Gn but may be stimulated by estradiol.Progesterone has a positive relation with prolactin.