Systolic blood pressure was measured at frequent intervals during the first 6 weeks of life in 99 normal neonates. Blood pressure rose from a mean of 70 mmHg at age 2 days, to 93 mmHg at age 6 weeks in babies awake; the majority of this rise (14 mmHg) took place in the first 2 weeks of life. The blood pressure measured when infants were asleep was lower than in those awake, but increased in a similar manner. Blood pressure of infants at 2 days was not significantly affected by method of delivery, or by the anaesthesia or analgesia that the mothers received in labour. It was not related to the Apgar score at one or five minutes.