The average normal incidence of superficial and deep-vein thromboembolic disease in women of childbearing age is 2.2 cases per 1,000 women per year. The incidence of this disease is not increased during pregnancy, when estrogen secretion is increased, or when oral contraceptives are employed. In over 80,000 women receiving oral contraceptives for more than 1,000,000 cycles the incidence of superficial and deep-vein thromboembolic disease is 0.97 cases per 1,000 women per year. Retrospective survey studies have provided the hypothesis of increased risk in women taking oral contraceptives, but this hypothesis is not confirmed by the large volume of prospective data. Available data do not demonstrate that women with a history of thromboembolic disease are more susceptible to a recurrence when using oral contraceptives, and women developing thrombophlebitis have recovered uneventfully while continuing to use oral contraceptives.