Objectives: To investigate the importance of β-hCG values on the day of onset and on the fourth and seventh day after treatment in the effectiveness of treatment in tubal ectopic pregnancies treated with a single dose of methotrexate (MTX). Material and methods:One hundred sixty-two patients with tubal ectopic pregnancy treated with a single dose MTX treatment were retrospectively evaluated. β-hCG values and changes on Days 0, 4 and 7 of the MTX treatment successful group and the unsuccessful group were analyzed.Results: MTX treatment was successful in 125 (77.2%) and unsuccessful in 37. When the β-hCG values on Days 0, 4 and 7 were compared in pairs, the differences between groups were statistically significant (p < 0.001).The mean β-hCG value was 783.0 in the MTX successful group and 1802.0 in unsuccessful group (p < 0.001). There was a 21.6% decrease in β-hCG values between Days 0 and day 4 in the MTX successful group and a 25.7% increase in the MTX unsuccessful group (p < 0.001). On Days 0, 4 and 7, ROC curve analysis's values are , respectively; 755/939/486 for cut off, 86.49/83.78/94.59% for sensitivity and 48.80/69.60/72.36% for specificity. Conclusions:Success rates of single-dose MTX treatment increase in tubal ectopic pregnancies with low initial β-hCG value. Patients with a decrease in β-hCG value and/or a cut-off decrease of 20% or more on the fourth day of treatment can be called for weekly β-hCG monitoring without the need for close follow-up. The change in β-hCG between Day 0 and Day 4 can be used to predict the efficacy of treatment.