['To investigate the relationship between follicular blood flow and the follicular fluid vascular endothelial growth factor (VEGF) and nitric oxide (NO) concentrations and to determine which factor might be a better predictor of the outcome of IVF-ET.', 'Prospective study.', 'Academic research laboratory.', 'Forty-seven cycles of IVF (tubal factor, 25 cycles; male factor, 22 cycles) at the infertility clinic of Pusan National University Hospital from February 2002 to June 2002.', 'Follicular blood flow was estimated on the day of hCG administration. Each follicular fluid sample was collected at oocyte retrieval, and follicular fluid VEGF and NO concentrations were assessed.', 'Follicular blood flow and follicular fluid VEGF and NO concentrations according to the age of patients, the cause of infertility, and pregnancy rate.', 'Of 47 cycles, 18 (38.3%) cycles resulted in a pregnancy. Follicular blood flow was significantly higher in the pregnant group compared with the nonpregnant group, but there was no statistically significant difference in age and infertility cause. Follicular fluid concentrations of VEGF and NO did not show statistically significant differences in age, infertility cause, or pregnancy outcome. As the follicle size increases, the follicular blood flow and follicular fluid VEGF concentrations increased significantly but the follicular fluid NO concentrations decreased. There was no correlation between VEGF and NO concentrations in the follicular fluid by linear regression analysis.'] Is follicular blood flow a better predictor of the outcome of in vitro fertilization-embryo transfer than follicular fluid vascular endothelial growth factor and nitric oxide concentrations?