Purpose of investigation: The aim of this study was to evaluate the correlation between endometriosis and pathologies on an immune basis for the possible involvement of the immune system in the pathogenesis of endometriosis. Materials and Methods: In this retrospective study, data of 304 patients with endometriosis and 318 without endometriosis were collected in a uniform manner for both groups and inserted into two databases, respectively, for patients with and without endometriosis. The authors calculated the percentages of patients with allergies, autoimmune diseases, asthma in both groups, and later statistical analysis were performed with two different chisquare tests. Results: The results obtained have shown that patients with endometriosis have a higher prevalence of allergies (p = 0.0003) and coexistence of both allergies and autoimmune diseases (p = 0.0274), compared to those without. Conclusions: The present study seems to support the possible association between endometriosis and allergic diseases.