Background: Endometriosis is often defined as heterogeneous immune abnormality. In accordance with the data, women with endometriosis are more frequently affected by Hashimoto’s thyroiditis, systemic lupus erythematosus, Sjögren syndrome, rheumatoid arhritis, asthma, eczema and have increased activity of policlonal B-cells, abnormal acitvity of T- and B-lymphocytes, decreased activity of natural killer cells and presence of antiendometrial antibodies. In our study, we tried to define the disease in the context of other autoimmune diseases and determine the type of immune abnormality. Methods: In the prospective study 60 females with endometriosis were inluded in the study group and 49 healthy females in the control group. The presence of endometriosis in the complex of other autoimmune diseases was evaluated by targeted family, personal and reendomeproductive history. The type of immune abnormality was evaluated by immunological analysis on the cell level: subtypisation of lymphocytes, cytotoxic and regulatory T cells and NK cells. On the humoral level, we defined antiovary, antiendometrial and antiendothelial antibodies. The results were statistically evaluated using the Pearson’s Chi-square test and Mann – Whitney test. Results: Patients with endometriosis are more frequently affected by allergies (p = 0.039). Five serums of endometriosis patients were positive for antiendothelial antibodies specifically reacting with vascular endothelium. There was statistically significant diference between the study and the control group in the proportion of regulated T lymphocytes (CD3+ CD25++) in the pherypheral blood (p = 0.025). Conclusions: We have not fully confirmed the hypothesis that women with endomeriosis have alterations in the immune response. However, the present study supports and adds important infomation to the views that immune abnormality plays an important role in the etiopathogenesis of endometriosis. On the humoral level, we showed the presence of antiendothelial antibodies reacting with vascular endothelium.