The course and outcome of 169 pregnancies in 156 women with chronic hypertension were studied. Antihypertensive medications were given if the diastolic blood pressure exceeded 90 mmHg. A number of major associated medical problems were found. Left ventricular hypertrophy, a serum creatinine greater than 1.0 mg%, and a diastolic pressure greater than 100 mmHg at less than 20 weeks' gestation were high-risk indicators. The overall perinatal mortality was 28.4 of 1000 (versus hospital of 25.6 of 1000). Despite antihypertensive therapy, one-third of the patients developed superimposed preeclampsia. The poorest outcome occurred in patients with superimposed preeclampsia necessitating delivery at 27 to 34 weeks' gestation (perinatal mortality = 238 of 1000). Antepartum fetal heart rate testing was abnormal in 10% of the patients with intrauterine growth retardation occurring in 15%. The incidence of fetal growth retardation was fourfold higher (20 versus 5%) in patients treated with antihypertensive drugs, particularly methyldopa as a single agent. However, this may have been related more to the study design than to a detrimental effect of the drug. The perinatal outcome in this study is similar to the outcome of studies in which antihypertensive therapy was withheld. This indicates that controlling the blood pressure is merely one aspect of the management of chronic hypertension in pregnancy. Accurate dating, attention to associated medical problems, antenatal fetal assessment by ultrasound and heart rate monitoring, and carefully timed delivery are additional important factors.