Endometriosis, adenomyosis and leiomyomata develop in women of reproductive age and regress after menopause or ovariectomy, suggesting that they grow in an oestrogen-dependent fashion. We investigated whether polymorphism in the oestrogen receptor-alpha (ERalpha) gene is related to oestrogen-dependent benign uterine disease. A total of 203 women with regular menstrual cycles underwent laparotomy or laparoscopy and were diagnosed histologically with endometriosis, adenomyosis and/or leiomyomata. Patients with cervical carcinoma in situ, tubal occlusion or adhesion but no other gynaecological disease were considered to be disease-free. A total of 179 women undergoing annual health examination were grouped as reference population. The distribution of PVUII genotypes (PP, Pp, and pp) of the ERalpha gene was different between each pair of the four groups of endometriosis, adenomyosis/leiomyomata, disease-free, and reference population (P = 0.022-0.0005), except between the former two groups. The PP genotype was less frequent in the groups of endometriosis (P = 0.0002) and adenomyosis/leiomyomata (P = 0.002) as compared to that in the disease-free group. In the endometriosis group, there was no difference in the distribution of PVUII genotypes due to complicating diseases (adenomyosis and/or leiomyomata) or severity of the clinical stages. These results suggest that the PVUII polymorphism of the ERalpha gene is associated with the risk for endometriosis, adenomyosis, and leiomyomata.