In order to explore the correlation between endometriosis and beta-Endorphin, Dynorphin, the beta-Endorphin and Dynorphin levels in menstrual blood of normal women and patients with endometriosis, and the pituitary-hypothalamic beta-Endorphin and Dynorphin levels in animal models were determined. The results indicated: (1) The plasma beta-Endorphin and Dynorphin levels in patients with endometriosis were significantly lower than those in normal women (P < 0.05); the plasma beta-Endorphin levels in patients with endometriosis were significantly higher after treatment of Endometriosis Pill No. 2 (P < 0.05). (2) The pituitary and hypothalamic beta-Endorphin levels in untreated group were significantly higher than those in the control group (P < 0.05); the hypothalamic beta-Endorphin in treated group were obviously higher than those in untreated group (108.35 +/- 35.38 and 66.63 +/- 14.29 respectively). The above-mentioned results presented evidence that the low beta-Endorphin and Dynorphin levels in endometriotic patients play a role in dysmenorrhea; the effect of Endometriosis Pill No. 2 in relieving dysmenorrhea was realized through an increase of plasma and hypothalamic beta-Endorphin levels. (3) The Pituitary and hypothalamic beta-Endorphin levels were significantly different between the animal models of endometriosis and normal control groups.