In order To evaluate whether the parameters of spiral artery blood flow, as measured by transvaginal color Doppler, may be used to assess endometrium receptivity prior to embryo transfer (ET), a retrospective study of 94 infertile women who had undergone ART treatments with different outcomes (pregnant or nonpregnant) was done. Subendometrial blood flow was evaluated. The resistance index (RI), systolic/diastolic ratio (S/D) and pulsatility index (PI) were significantly lower in those who achieved pregnancy as compared with those who did not: 0.62+/-0.04 vs 0.68+/-0.04 (P<0.001), 2.66+/-0.33 vs 3.19+/-0.39 (P<0.01) and 1.15+/-0.17 vs 1.34+/-0.22 (P<0. 05), respectively. Furthermore, when RI>0. 2, PI>1. , and S/D>3. , no pregnancy occurred. These data suggest that the parameters of spiral artery blood flow could be used as a new assay in predicting endometrial receptivity before ET.