1. The mean blood pressure runs a curvilinear pattern during the course of pregnancy, with the lowest reading between 20 and 27 weeks of gestation, a continuous rise from 28 to 36 weeks, followed by a plateau. 2. the mean blood pressure in pregnancies without edema and proteinuria are lowest throughout pregnancy. However, the mean blood pressures in pregnancies complicated by edema, proteinuria, or both, are less than 5 mm. Hg higher after 28 weeks of gestation. 3. The mean blood pressures are lower in black gravidas than in white gravidas throughout pregnancy, independent of the presence or absence of edema, proteinuria, or their combinations. 4. The mean blood pressure is related to age and parity. Median-age gravidas (20-34 years) of parity 1-5 have the lowest mean blood pressures overall at any time during gestation. The mean blood pressure of nulliparas, independent of age, is elevated over the mean blood pressure of comparable multiparas. Independent of parity, maternal age systematically affects the mean blood pressure. 5. The standard deviations for the mean diastolic and systolic blood pressures are approximately 9 and 11 mm. Hg, respectively, independent of the weeks of gestation. They are affected very little by the absence or presence of edema or proteinuria, or both. 6. Edema of hands and/or face occurs more often in black gravidas. 7. The overall perinatal mortality rates in pregnancies complicated by edema are not higher than in pregnancies without edema. Perinatal mortality rates in pregnancies with proteinuria, or edema and proteinuria, on the other hand, are approximately double the rates for pregnancies without edema and proteinuria.