Background: Systemic lupus erythematosus (SLE), along with autoantibody production, is undeniably associated with levels of female sex hormones, specifically E2. Beneficial effects of D vitamin on the course of autoimmune disorders have been confirmed through numerous studies, while the effect of inflammatory cytokines, especially IFN-γ, is still under study. Objectives: The aim of this study was to determine the serum levels of 25-hydroxy-vitamin D3, oestradiol and interferon-gamma in female SLE patients of childbearing age with inactive disease, as well as their interconnection. Methods: In total, 36 SLE and 37 control subjects were enrolled in the study. Serum concentrations of 25-OH D3, E2 and IFN-γ were measured by radioimmunoassay using a gamma-counter and enzyme-linked immunosorbent assay. Results: The concentration of 25-OH D3 was lower in SLE patients compared to the control group (p=0.001), while E2 was higher (p<0.001). In vitamin D deficient (25-OH D3 ≤ 20 ng/ml) SLE patients, IFN-γ was 150% higher compared to patients with 25-OH D3 > 20 ng/ml and the control group (p=0.008). The concentration of E2 was greater in all SLE patients compared to the control group, independent of the vitamin D level (p=0.009 and p=0.035, respectively). We found a positive correlation between E2 and IFN-γ in SLE patients and the control group (p=0.027and p<0.05, respectively). Vitamin 25-OH D3 positively correlated with dsDNA and Sm antibodies, while E2 was positively correlated only with dsDNA antibodies. Conclusions: Concentration of oestradiol and IFN-γ was elevated in SLE patients with inactive disease, while the concentration of vitamin D was decreased compared to healthy subjects. IFN-γ was elevated with decreased levels of vitamin D, which may indicate protective role of vitamin D in autoimmune inflammation. This study promotes the significance of learning the interaction between vitamin D, E2 and IFN-γ in understanding and monitoring the SLE.