Background Endometrial polyps (EPs) occur in approximately 34.9％ of infertile women.Transvaginal sonography (TVS) is a routine,non-invasive component of fertility evaluation.Most ultrasonographic studies of EPs have focused on abnormal uterine bleeding; few have assessed EPs in infertile women.Furthermore,no studies have explored endometrial thickness and its correlation with EPs in infertile women.This study aimed to assess transvaginal sonographic assessment of endometrial thickness and its value in diagnosis and prediction of EPs in infertile women.Methods A retrospective study on 314 infertile women was conducted from June to December 2010.After TVS,endometrial biopsies were obtained by hysteroscopy.Pathologically confirmed EPs were taken as the gold standard.Results Based on recognized criteria,TVS had a sensitivity of 37.04％,specificity of 98.71％,positive predictive value of 90.91％,negative predictive value of 81.85％,and accuracy of 82.80％ for diagnosing EPs.Mean endometrial thickness was significantly different in patients with and without EPs (P=0.0001).In women in the mid and late-proliferative phase,the endometrial thickness was significantly greater in those with EPs than in those without them (P=0.0001 and 0.024).Receiver operating characteristic analysis showed that endometrial thickness had a sensitivity of 85.2％ and specificity of 38％ in the diagnosis of EPs,the area under the curve being 0.64.In the mid-proliferative phase,sensitivity was up to 90.9％,the area under the curve being 0.70.Conclusions rvs is poor at detecting EPs in infertile women; however,transvaginal sonographic measurement of endometrial thickness is helpful.It is suggested that the diagnostic value of TVS for EPs in infertile women could be improved by adding the measurement of endometrial thickness to the variables that are routinely assessed.