An association between minor endometriosis and subfertility is shown by prevalence studies but a clear causal relationship has not yet been demonstrated. This review presents the evidence for pituitary-ovarian dysfunction as a cause for subfertility in women with minor endometriosis. Using tubal infertility cases as controls, group comparison has shown effects on the following: follicular growth (impaired) , preovulatory circulating oestradiol levels (reduced) and early luteal phase oestradiol and progesterone (reduced) , and LH surge patterns (disordered), preovulatory follicular fluid LH concentration (reduced) , and granulosa cell steroidogenic capacity (impaired) . However, these findings are not consistent in the literature. Compared with controls, reduced oocyte fertilisation and implantation rates are reported in natural and go-nadotrophin stimulated cycles. An inherent disorder of follicular function is possible as a cause, with LH surge impairment probably a secondary phenomenon. Natural sub-fe An association between minor endometriosis and subfertility is shown in prevalence studies but a clear causal relationship has not yet been demonstrated. This review presents the evidence for pituitary-ovarian dysfunction as a cause for subfertility in women with minor endometriosis. Using tubal infertility cases as controls , group comparison has shown effects on the following: follicular growth (impaired), preovulatory circulating oestradiol levels (reduced) and early luteal phase oestradiol and progesterone (reduced), and LH surge patterns (disordered), preovulatory follicular fluid LH concentration (reduced) Compared with the reduced oocyte fertilization and implantation rates are reported in natural and go-nadotrophin stimulated cycles. An inherent disorder of follicular function is possible as a cause, with LH surge impairment probably a secondary phenomen on. Natural sub-fe