The significance of these and related data will be discussed in greater detail during the subsequent course of this workshop. For now, we can sum up our findings with the following general statements concerning this analysis: 1. Blood pressure elevation occuring alone during the course of pregnancy, in the absence of edema and/or proteinuria, affects perinatal survival adversely. 2. This relationship is most marked among nulliparas in the age range 20-34 years and is less pronounced, but still evident, in young nulliparas and in multiparas of comparable age. 3. The effect is greater among black patients than among white patients in the median-aged nulliparas and multiparas, but this difference is not mirrored in the young nulliparas studied. 4. Blood pressure elevations during weeks 20-28 of pregnancy result in much higher subsequent perinatal losses in white nulliparas (both median and young age groups) than comparable elevations earlier or later in pregnancy. 5. Among black nulliparas of median age, maximal blood pressure effect on outcome is encountered at the sixteenth week (the earliest available data), with continuing significant increases until the twenty-eighth week, and there is another increment at term. In younger black patients, the results from 20 through 28 weeks parallel those seen in white patients, but with an additional peak at term. 6. among multiparas, maximal effect occurs at 24-28 weeks in both black and white groups. 7. The critical blood pressure levels are significantly lower in early pregnancy than in late pregnancy. 8. Critical levels of blood pressure with advancing pregnancy appear to parallel the trend in mean blood pressures determined to exist for this series. 9. Utilizing blood pressure distribution data to set limits statistically, we find very meaningful increments in perinatal mortality rates for nulliparas presenting blood pressure elevations beyond the 95 percentile point. This holds also for diastolic or systolic levels when these are examined independently because neither alone yielded more convincing data than blood pressure combinations condidered together.