PIP: Large prospective epidemiologic studies have shown that long-term use of oral contraceptives containing estrogen induce an increase in blood pressure and sharply increase the risk of hypertension. Susceptibility to the hypertensive effects of oral contraceptives is heightened where risk factors such as age, family history of hypertension, preexisting or occult renal disease, parity and obesity exist. Hypertension among pill users usually develops within the first 6 months of usage and occasionally is delayed for as long as 6 years. Anitihypertensive therapy is seldom needed as the hypertension that developes is generally mild and uncomplicated, and rapidly reverses when the pills are discontinued. However, a small percentage of patients develop severe, even life-threatening hypertension and the hypertensive effects are felt long after the pills are discontinued. Cases of malignant hypertension and irreversible renal failure requiring maintenance hemodialysis, bilateral nephrectomy, and renal transplantation have occurred following administration of oral contraceptive pills. The mechanism by which oral pills induce hypertension in susceptible women is not known and needs further research. Before oral contraceptives are prescribed, physicians should take a careful history and perform a detailed physicial examination with special attention to the cardiovascular system. Multiple blood pressure measurements should be made and routine laboratory studies including urinalysis, blood urea and nitrogen and serum creatinine should be performed. It is preferable to start with a relatively low (50 mcg) estrogenic content preparation. Patients who develop hypertension (diastolic pressure, 90 mm Hg) on oral contraceptives should stop taking the pills immediately, and should be considered to have estrogen-induced hypertension. They should never again receive estrogen-containing oral pills, although they can try pills containing only progestogen. There is no contraindication to pregnancy in these patients, as most women who become hypertensive on oral pills go on to have normotensive pregnancies. Pregnancy in women who are susceptible to essential hypertension however should be treated as high risk.