The predominant symptom for endometriosis is pain. The presence of nitrosative stress in the eutopic and ectopic endometrium may cause the pathological mechanism of pain through increased expression of neuropeptides. Objective — to evaluate the contribution of nitrosative stress in enhancing the expression of neuropeptides and the implementation of pain in patients with endometriosis. Material and methods. ELISA was used to determine the content of NOS, UCHL1, VIP in peritoneal fluid and in the blood; immunohistochemistry was used to assess the expression of nNOS, iNOS, VIP in vessels, UCHL1 and VIP densities; western blot was used to assess the expression of the protein nNOS, UBLH1, VIP; polymerase chain reaction was used to assess the expression of mRNA nNOS, mRNA UBLH1, mRNA VIP in eutopic and ectopic endometrium in patients with endometriosis and pelvic pain. Results. A comparative analysis of the content of NOS, UCHL1, VIP (ELISA, enzyme-linked immunosorbent assay) in the peritoneal fluid and in the blood; expression of nNOS and iNOS, VIP in vessels, density of UCHL1 and VIP (IHC, immunohistochemistry), expression of nNOS protein, UBLH1, VIP (WB, Westrn blot), expression of mRNA nNOS, mRNA UBLH1, mRNA VIP (PCR, polymerase chain reaction ) in eutopic and ectopic endometria in patients with endometriosis and pelvic pain a statistically significant increase in the studied parameters was shown. Conclusion. At the proteomic and transcriptomic levels, the role of nitrosative stress due to neuronal and inducible nitric oxide synthase has been proven to enhance the expression and accumulation of VIP and UCHL1 neuropeptides in eutopic and ectopic endometrium and in peritoneal fluid in patients with endometriosis and pelvic pain. The results can be used to assess the contribution of nitrosative stress in the implementation of pain in endometriosis and the choice of treatment tactics.