To examine the relationship between serum total oxidant (TOS) and antioxidant (TAS) levels and clinical pregnancy in assisted reproductive technology (ART) cycles.Prior to and after oocyte pick-up (OPU) and embryo transfer (ET), blood samples were collected from gynecologically normal females (n = 70) who were enrolled for ART solely due to male factor infertility. TAS, TOS levels and oxidative stress indexes (OSI: TOS/TAS) in four phases of treatment cycle (pre and post OPU and ET) between clinically pregnant and non-pregnant patients were compared. Critical cut-off values of significantly different TAS, TOS levels and OSIes for clinical pregnancy were established.The TAS levels in patients with clinical pregnancy were significantly higher in all of the four phases of the cycle. Post-OPU and pre-ET TOS levels were significantly higher in clinically pregnant patients. According to OSIes; only the pre-OPU OSI was significantly lower in clinically pregnant patients compared with non-pregnant ones. Moreover, the highest area under the ROC curve (AUC) from the seven different significant measurements [1) pre-OPU OSI, 2) pre-OPU TAS, 3) post-OPU TAS, 4) pre-ET TAS, 5) post-ET TAS, 6) post-OPU TOS, 7) pre-ET TOS] was related to pre-OPU OSI.In ART cycles, women with a higher total antioxidant status prior to and after OPU and prior to and after ET have an increased probability of clinical pregnancy. Additionally; OSI before OPU was one of the most important determinants for clinical pregnancy, so the oxidant and antioxidant balance is as important as the antioxidant concentration alone.