Pigmentary demarcation lines are borders of abrupt transition between more deeply pigmented skin and that of lighter pigmentation. We describe two patients with pigmentary demarcation lines associated with pregnancy symrnetrially involving the buttocks and flexor as jects of legs. Hormonal changes in pregnancy and compression by the enlarged uterus of Sl and S2 peripheral nerves may be responsible for these changes. (Kor J Dermstol 1994;32(5):903-906)