OBJECTIVE The aim of this study was to investigate the thiol/disulfide homeostasis in tubal ectopic pregnancies in terms of early diagnosis of the disease. METHODS A prospective case-control study was carried out between June 2017-February 2018 in the Gynaecology Department of Umraniye Medical and Research Hospital. METHODS A total of 42 women with ectopic pregnancy were compared with 44 healthy women who have intrauterine first trimester pregnancies. The thiol/disulfide homeostasis is evaluated with the spectrophotometric measurement method that was recently developed by Erel&Neselioglu. RESULTS Disulfide/native thiol and disulfide/total thiol ratios were increased (p = 0.018 and p = 0.023 respectively), while native thiol/total thiol ratios and native thiol levels were decreased in tubal ectopic pregnancy group according to control group (p = 0.023). Between control and tubal ectopic pregnancy groups no differences were measured in disulfide levels (p = 0.350). The area under curve for native thiol and total thiol were 0.937 and 0.927, respectively. The optimum cut off value for native thiol was 379.95 μmol/l with a sensitivity of 90% and specificity of 81%. The optimum cut off value for total thiol was 432.5 μmol/l had 92% sensitivity and 79% specificity. CONCLUSIONS In the study, whether intrauterine pregnancies resulted in miscarriage or delivery can be examined. CONCLUSIONS Increased disulfide/native thiol levels, disulfide/total-thiol ratio and decreased native/total thiol ratio were found to be significantly associated with the presence of tubal ectopic pregnancy which can be useful for the early diagnosis of the disease.