['To determine whether the anti-Müllerian hormone (AMH) level in follicular fluid is associated with success in oocyte fertilization during in vitro fertilization (IVF) cycles.', 'Retrospective study.', 'Tokyo Medical University hospital.', 'Thirty-one women undergoing IVF cycles.', 'The women were divided into two groups according to the success or failure of fertilization. Follicular fluid samples were obtained from a single follicle in each patient.', 'Assessment of values for AMH, inhibin B, and estradiol from follicular fluid and serum on the day of oocyte retrieval during IVF treatment.', 'The follicular fluid AMH levels from fertilized patients (group 1) were 3.42 times higher than from nonfertilized (group 2). There was no correlation between the ratio of the high quality grade embryos and either serum AMH or inhibin B levels. There was no statistically significant correlation between serum AMH and the number of oocytes. However, there was a strong correlation between levels of serum estradiol, inhibin B, and the number of oocytes.'] Is anti-Müllerian hormone substance from follicular fluid positively associated with success in oocyte fertilization during in vitro fertilization?