1 The pharmacological properties of atenolol suggest its possible usefulness in pregnancy-induced hypertension. The pharmacokinetics of atenolol in the pregnant woman, concentrations in cord blood, and its effects on maternal blood pressure and the foetus, are evaluated. 2 We studied 13 pregnant women with hypertension, most of them uncontrolled on methyldopa. Whole blood concentrations and urinary excretion of the drug were measured over 24 h following a 100 mg dose. Effects on maternal blood pressure, pulse rate and foetal heart rate and cardiotocograph were compared for the 4 days before treatment and the first 4 days of treatment. The birth weights and Apgar scores of the babies were recorded. 2 The pharmacokinetics of atenolol (plasma half-life of about 8 h) in pregnant women do not differ from the findings in the non-pregnant. The levels of atenolol in the cord blood were confirmed as approximately equal to those in the maternal blood. 4 In the ten women in whom blood pressure was assessed a small significant fall in blood pressure was observed. 5 A 5% mean fall in foetal heart rate resulted but in one case was a rate below 120 beats/min recorded. There was no evidence of depression of the stress response of the foetal heart. Apgar scores 5 min post partum were satisfactory. 6 Atenolol appears to be safe for use in hypertensive pregnancies. Its effectiveness as an antihypertensive agent in pregnancy requires further controlled evaluation.