The authors investigated the expression patterns of interleukin (IL)-lβ and tumor necrosis factor (TNF)-α, cytokines associated with peritoneal inflammatory reactions, and of B cell leukemia lymphoma (Bcl)-6 and B lymphocyte inducer of maturation program (Blimp)-1, transcriptional factors associated with immunoglobulin (Ig) production; the concentrations of Igs, and their correlation, in patients with and without endometriosis.The authors analyzed the peritoneal fluid of 98 patients, 46 with endometriosis, and 52 with benign tumors.IL-1 and TNF-α mRNAs and IgG and IgA concentrations were higher in the endometriosis group, but the differences were not statistically significant. However, Bcl-6 mRNA level was significantly lower and Blimp-1 mRNA level was significantly higher in the endometriosis group with significant correlations among transcriptional factors, Igs, and cytokines (p0.05).Peritoneal immune responses in patients with endometriosis may be due to increased IgG and IgA concentrations, as well as to changes in expression of proinflammatory cytokines and transcriptional factors.