To evaluate whether a combination of putative markers of inflammation and CA-125 could serve as a multiple-marker screening test for endometriosis in a heterogeneous population of patients.Case-control evaluation of a diagnostic test.University medical center.Consenting women of reproductive age undergoing laparoscopy for indications of pain, infertility, elective tubal ligation, tubal reanastomosis, or other benign indications.Diagnostic laparoscopy and peripheral venipuncture.Serum concentrations of interleukin-6, tumor necrosis factor-alpha, macrophage migration inhibitory factor, macrophage chemotactic protein-1, interferon-gamma, leptin, and CA-125 measured by using ELISA assays; surgical staging of endometriosis.Concentrations of the seven markers were compared between the 63 women with surgically confirmed stage II-IV endometriosis and 78 women who were surgically confirmed to be free of endometriosis. The individual diagnostic performance of each of the markers, based on receiver operating characteristic curves, was poor. When combinations of markers were evaluated by using classification tree analysis, a three-marker panel of CA-125, macrophage chemotactic protein-1, and leptin could diagnose 51% of subjects as to the presence of endometriosis with 89% accuracy. A four-marker panel of CA-125, macrophage chemotactic protein-1, leptin, and macrophage migration inhibitory factor could diagnose 48% of subjects with 93% accuracy. The remaining subjects would have no definitive diagnosis on the basis of the algorithm and would need to undergo standard evaluation.This large study evaluates the combined use of putative serum markers for the diagnosis of endometriosis, rather than the use of each singly. Using the serum concentration of four markers in a two-tiered decision rule, nearly half of the subjects in this population would have been diagnosed (and could have avoided surgery) with 93% accuracy.