To investigate the evaluation of the early follicular phase serum inhibin B levels as indicator of ovarian reserve and treatment options in the field of reproductive medicine. Retrospective analysis. 361 women aged 21–42 years (mean 31) with different infertility etiologies of in vitro fertilization and embryo transfer (IVF-ET) were investigated. Serum levels of follicle stimulating hormone (FSH), luteinizing hormone (LH) by chemiluminescent microparticle immunoassay and inhibin B by ELISA were measured in the third day of a spontaneous menstrual cycle, estradiol (E2) was measured on the day of HCG administration by the same way of FSH. Patients generally underwent gonadotrophin releasing hormone agonist down-regulation followed by exogenous gonadotrophin stimulation. These patients were classified into three groups including poor response (n = 76), normal response (n = 262), and over response (n = 23) according to their response to ovary stimulation, which base on the number of oocytes retrieved (n ≤ 4; 5 ≤ n≤19; n ≥ 20). In three groups, inhibin B concentration, FSH level, E2 on HCG day, the number of retrieved oocytes, quality embryos, pregnancy rate, and the dosage of recombined FSH are different. In stepwise regression analysis, inhibin B and FSH, FSH/LH ratio correlate negatively (r = −0.287, −0.451 respectively; P<0.05). While E2 on HCG day, the number of retrieved oocytes, quality embryos correlate positively with inhibin B serum concentrations (r = 0.369, 0.454, 0.376 respectively; P<0.05).TableComparison of hormone levels, rFSH dosage and clinical results in three groupsGroupsInhibin B(pg/mL)FSH(IU/L)E2 on HCG Day(pg/mL)Dosage of rFSH(IU)No of oocytesPregnancy rate/cyclePoor response28.2 ± 15.610.2 ± 4.72450.1 ± 1408.33228.0 ± 1398.03.3 ± 1.414.5Normal response79.4 ± 41.3∗7.7 ± 4.2∗3460.9 ± 2053.1∗2542.5 ± 858.0∗11.8 ± 3.5∗36.1∗Over response99.3 ± 69.1∗6.9 ± 1.1∗8204.0 ± 2574.2∗2093.3 ± 461.3∗21.8 ± 2.1∗21.71∗P<0.05 vs. poor response group; 1 fresh embryo transfer was cancelled in 8.7% cycles of over response group because of ovarian hyperstimulation syndrome. Open table in a new tab ∗P<0.05 vs. poor response group; 1 fresh embryo transfer was cancelled in 8.7% cycles of over response group because of ovarian hyperstimulation syndrome. During assisted reproductive cycles, inhibin B at baseline is associated with pregnancy, and being as strong predictive factor of ovary reverse, which is of clinic importance in the guidance of treatment options.