is of unexplained infertility (UEI) is made by exclusion and a relatively common problem that affects couples worldwide. Unfortunately, it is not uncommon for females to suffer from Hashimoto's thyroiditis (HT). Interferon-gamma (IFN- γ) has a central key role in HT and in the ability to conceive. We aimed to estimate serum IFN- γ level and its expression profile in Egyptian women with HT and assess their possible association with UEI. In this study, we examined 120 women with HT. We evaluated fertility in all patients; female patients who suffer from UEI were detected. Diagnosis of HT was based on the clinical data and the laboratory measures, enzyme-linked immunosorbent assay was used to measure serum IFN￾γ, and the expression of IFN-γ messenger ribonucleic acid (mRNA) was assayed by real-time polymerase chain reaction (PCR). According to the results of this study, 37.5 % of the studied females who suffered from HT were diagnosed with UEI. The serum level of IFN-γ and its gene expression showed a significant positive correlation with thyroid-stimulating hormone (TSH) and thyroid autoantibodies. However, a negative correlation was found with anti-müllerian hormone (AMH), free T4 (FT3), and free T4 (FT4). Analysis by linear regression revealed that TSH and FT3 were associated with serum level of IFN-γ; while FT3 was associated with IFN-γ gene expression. We concluded that both are valued markers in diagnosing UEI in female patients suffering from HT.