Objective To study the expression of KISS-1 in normal endometrium and in ectopic endometri-um patients with endometriosis. Methods The expression of KISS-1 in 55 cases of normal endometrium as well in 46 cases of ectopie endometriurn with endometriosis were detected by immunohistochemicai EliVision plus method. Results The positive expression rates of KISS-1 in ectopic endometriotic tissues and in normal endometri-urn were 30.43 % and 63.64 % respectively ,and the positive expression rates in ectopic endometriotic tissues signifi-cantly lower than those in the normal endometrium( P< 0.01, P < 0.05). Conclusion The decreased expression of KISS-1 may be related to the mechanism of endometriosis.