Fifty-three pregnant women with moderately severe hypertension were randomly allocated to treatment with methyldopa or oxprenolol. There were no significant differences between the groups in age, height, weight, parity, or stage of gestation at the start of treatment. The outcome of pregnancy was better in the group treated with oxprenolol, with greater maternal plasma volume expansion and placental and fetal growth. No intrauterine deaths occurred in either group, and antepartum fetal distress, detected by oxytocin challenge testing, was evident in only one patient, who received methyldopa. This infant, and one other in the methyldopa group, died in the neonatal period. No neonatal deaths occurred in the oxprenolol-treated group. Even in this small number of patients these results were considerably better than those in untreated women with hypertension of similar severity. Apgar scores in both groups were equivalent at birth, while blood sugar concentrations were higher in the oxprenolol group. Oxprenolol appears to be safe and effective in controlling hypertension during pregnancy. There was no evidence of harmful effects on the fetus, and oxprenolol may offer a selective advantage over methyldopa for fetal growth and wellbeing in utero.