Endometriosis is an estrogen-related chronic condition which consists in the implantation and growth of endometrial cells outside the uterine cavity. It has an immune and inflammatory background, and to-date the precise etiopathogenesis of endometrial cysts has not been unequivocally defined. The objective of the study was evaluation of the indicators of the inflammatory state, including RANTES and the levels of C-reactive protein, leukocytes, fibrinogen and iron in the blood serum of patients with endometrial cysts (n=48) and benign ovarian tumours of mature teratoma type (n=38). Statistical analysis was performed using the Mann-Whitney Rank Sum Test. The p values p<0.05 were considered statistically significant. Results: While comparing the results, respectively in groups, the mean levels in blood serum were as follows: RANTES 31,429.79 pg/ml (from 26,576.6 – 99,605.00) vs. 26,988.72 pg/ml (from 26,013.58 – 113,435.00) for p=0.428; CRP and WBC 2.13 vs. 1.54 mg/l; p=0.076 and 5.35 vs. 6.7; p=0.029; fibrinogen 3.12 vs. 2.57 mg%; p<0.001); iron level 87.20 vs. 78.01 ug/dl for p=0.430, and CA-125 36.50 vs. 15.08 U/ml; p<0.001). Conclusions: Statistically significant differences were observed in the levels of WBC, fibrynogen and CA-125 in blood serum. Therefore, the role of the inflammatory factor in the etiopathogenesis of endometrial cysts still remains unexplained, and the presented study may emerge as pioneer investigations in the area of etiology of endometriosis.