The aim of this study was to determine serum and peritoneal interleukin (IL)-2, IL-4, and monocyte chemotactic protein-1 levels as diagnostic markers of endometriosis in adolescent girls. The design of the study encompassed 50 adolescent girls, aged 13 to 19 years after menarche, with chronic pelvic pain who qualified for diagnostic laparoscopy. The patients were allocated into 2 groups: group I (endometriosis) consisted of subjects with diagnosed endometriosis (n = 33, 66%) and group II (control) whose laparoscopic examinations revealed no evidence of endometriosis (n = 17, 34%). IL-2, IL-4, and Monocyte chemotactic protein 1 concentrations in serum and peritoneal samples were assessed using commercially available human enzyme-linked immunosorbent assay kits. The results were analyzed statistically with the Statistica 8.0 computer software. The value of P < 0.05 was the level of statistical significance. The results in adolescents with endometriosis had significantly higher concentrations of serum IL-4 (3.90 ± 1.58 pg/mL vs. 3.04 ± 1.72 pg/mL; P = 0.04) and peritoneal fluid IL-4 (5.03 ± 8.92 pg/mL vs. 2.74 ± 1.11 pg/mL; P = 0.03), and lower peritoneal fluid IL-2 (92.44 ± 292.75 pg/mL vs. 174.23 ± 389.77 pg/mL; P = 0.01) compared with the control. In a receiver-operating characteristic analysis, serum IL-4 as well as peritoneal fluid IL-2 and IL-4 provided the best discriminative ability between subjects with endometriosis and controls. Using cutoff points for serum IL-4 (3.00 pg/mL), peritoneal fluid IL-2 (21.00 pg/mL) and IL-4 (2.7 pg/mL), relatively high odd ratios were obtained in the prediction of endometriosis in adolescents (3.2; 6.4; 3.3). The Serum IL-4, peritoneal IL-2 and IL-4 provided a good method of discrimination between subjects with endometriosis and controls.