Takayama et al. (1998) successfully treated one case of severe postmenopausal endometriosis with the aromatase inhibitor anastrozole. Fang et al. (2002) applied mice with targeted disruption of P450arom gene (ArKO, C57BL/6J background) (Fisher et al., 1998) to endometriosis study. Here, CYP19A1 is linked to endometriosis.