OBJECTIVES To evaluate and compare costs of belimumab treatment plus standard of care (SoC) vs SoC alone in patients with systemic lupus erythematosus (SLE). METHODS The cost analysis was conducted of the belimumab treatment plus SoC vs SoC alone for one year. Based on the results of clinical trials to assess safety and efficacy of belimumab (BLISS-52 and BLISS-76) the cost structure of treatment was determined. RESULTS The costs were evaluated in the following groups: drug costs, costs of inpatient and outpatient visits, costs for correction of adverse events and costs for treating of SLE complications. The costs of inpatient visits comprised 91,830 RUB/ 1,976 EUR for SoC alone and 52,991 RUB/ 1,140 EUR for patients treated with belimumab plus SoC. The correction of adverse events came to 7,763 RUB/ 167 EUR for SoC alone, while for belimumab plus SoC it was 7,846 RUB/ 169 EUR. The costs of treating SLE complications totaled 384,976 RUB/ 8,283 EUR and 370,229 RUB/ 7,966 EUR for SoC alone and belimumab plus SoC groups of patients, respectively. CONCLUSIONS The costs of inpatient visits in belimumab treatment group were lower than those of the SoC group resulting from a reduction in the frequency of SLE flare.  The costs for correction of adverse events were similar in both patients groups due to a good safety profile of belimumab. The level of costs for treating SLE complications was lower in belimumab as compared to that in SoC group as a consequence of lower frequency of cardiovascular, pulmonary, renal, and skin complications in the belimumab treatment group. A good safety profile and efficacy of belimumab, which had been demonstrated in clinical trials, led to a decrease in costs of inpatient visits and treatment of SLE complication in patients treated with belimumab.