The aim of this research was to expose the role of tumor necrotic factor alpha (TNF-Î±) in the pathogenetic endometriosis. This research had been done in dr. Muwardi Hospital Surakarta. Twenty patients undergoing laparoscopic operation because of endometriosis indication (Group I), 20 women (aged 23 to 40) who undergo interval sterilization by means of laparoscopic technique (Group II). During laparoscopic operation, peritoneal fluid is taken to examine TNF-Î± by ELISA technique. The results indicated that by independent t-test, a significant difference of concentration of TNF-Î± in the peritoneal fluid is found between endometriosis patients and normal women (who are sterilized) (P=0.00). By chi-square test, the Ratio Odds value 171 shows that the high concentration of TNF-Î± will increase the possibility of endometriosis 171 times rather than the low TNF-Î±. It could be concluded the high concentration of TNF-Î± is the risk factor of endometriosis in comparison with the low TNF-Î±. It shows that quite possibly TNF-Î± has a role in the pathogenic endometriosis.