Oral contraceptive-induced hypertension was observed in approximately 5% of users of higher dose pills. More recent evidence indicates that little increases in blood pressure can be observed even with 30 ??g estrogen, monophasic pills, contain those containing the new progestins. However, an increased incidence of clinically significant hypertension has not been reported. No significant clinical changes in blood pressure have been noted with any of the multiphasic formulations. It is possible for an occasional patient to experience an idiosyncratic reaction and develop hypertension; therefore, an annual assessment of blood pressure is still an important element of clinical surveillance, even when little dose oral contraceptives are used. Variables such as previous toxemia of pregnancy or previous renal disease do not predict whether a woman will develop hypertension on oral contraception. Likewise, women who have developed hypertension on oral contraception are not any more predisposed to develop toxemia of pregnancy.