Objective: Our purpose was to compare the estimated maternal cerebral perfusion pressure and an index of vascular resistance, the resistance area product, in nonpregnant women with hypertensive pregnant women. Study Design: The maternal middle cerebral artery was evaluated by transcranial Doppler ultrasonography in 17 nonpregnant women, 17 pregnant normotensive patients, 20 pregnant patients with chronic hypertension, and 21 pregnant patients with pre-eclampsia (defined by The American College of Obstetricians and Gynecologists criteria) and cerebral blood flow velocities were determined. We calculated estimated cerebral perfusion pressure as [Estimated cerebral perfusion pressure = V mean/(V mean = V diastolic) (Mean blood pressure – Diastolic blood pressure)] modified from Aaslid et al, 1986. Because the diameter of the vessels could not be measured directly, an index of resistance, the resistance area product, was calculated. Resistance area product = Mean blood pressure/mean velocity (Evans et al, 1988). We calculated an index of cerebral blood flow (Cerebral blood flow index) = Estimated cerebral perfusion pressure/resistance area product. Results: Women who were chronically hypertensive and those with pre-eclampsia showed a significant increase in estimated cerebral perfusion pressure and resistance area product compared with nonpregnant and pregnant normotensive women. An estimate of cerebral blood flow (cerebral blood flow index) in nonpregnant women showed that pregnancy resulted in a nonsignificant 18% increase in cerebral blood flow. Conclusions: Women with chronic hypertension and pre-eclampsia behave similarly by demonstrating significant increases in cerebral perfusion pressure (estimated cerebral perfusion pressure) and cerebrovascular resistance (resistance area product) compared with normotensive and nonpregnant women. Pregnant patients have a minimal increase in cerebral blood flow (18%). (Am J Obstet Gynecol 1998;179:1200-3.)