Intra-uterine heart arrhythmia, postpartal respiratory insufficiency, bradycardia and hypoglycaemia were observed in a premature infant (37 weeks gestational age) delivered by a caesarian section. The mother had been treated with adequate doses of labetalol because of pregnancy-induced hypertension and her plasma concentration was found to be 89 μg/1 one day after delivery. The half-life of labetalol in the plasma of the infant was found to be approximately 24 h, i.e. substantially longer than in normal adults. The half-life of labetalol in newborn premature infants may be prolonged as compared to normal adults. More studies are required regarding the pharmacokinetics of this agent in premature infants and newborn babies.