Objective To study the expression of nociceptin in adenomyosis tissue and understand its relationship with the severity of dysmenorrhea. Methods The myometrial specimens were collected from 55 patients undergoing hysterectomy at our hospital during December 2007 and June 2008. Their mean age was 41 -52 years old. There were 34 adenomyosis patients in case group and 21 other patients in control group. Immunohistochemical staining was employed to detect nociceptin in eutopic endometrium and ectopic endometrial tissues in case group and normal endometrium and myometrial tissues in control group. Results The expression of nociceptin was significantly higher in the eutopic endometrial tissue ( 7. 1 ± 1.7 ) of case group than those in endometrial(2.7±2.0 ) and myometrial tissues of control group ( P ＜ 0.05 ); The expression of nociceptin was higher in the eutopic endometrial tissue (7.4±1.5) of dysmenorrhea group than that of non-dysmenorrhea group ( 5.0 ± 1.2 ) in case group ( P ＜ 0.05 ); The expression of nociceptin in eutopic endometrium and myometrium was the highest in severe dysmenorrhea group ( 8.4 ±1.3 ). And the non-dysmenorrhea and mild dysmenorrheal groups had no significant differences [(5.0 ± 1.2 ) vs (6.8 ± 1.4)]. And it decreased gradually in moderate dysmenorrhea, mild dysmenorrhea and nondysmenorrhea groups. Conclusion A high expression of nociceptin in adenomyosis may be one of the casual factors of dysmenorrhea. The severity of dysmenorrhea is positively correlated with the expression of nociceptin in eutopic endometrial tissue in case group ( r = 0.515, P = 0.034) and ectopic endometrium tissue. And the endometrial expression of nociceptin may be monitored dynamically to track the development of adenomyosis.