The aim of the present study was to assess if there was an association between low catecholamine levels at birth in the premature infant and the development of TTN. Blood samples were collected at delivery from the umbilical artery of all preterm infants with a gestational age less than 36 weeks for determination of pH and catecholamine levels (noradrenaline and adrenaline). Amongst non-asphyxiated infants only, cord pH greater than 7.25 and/or Apgar score greater than 7 at five minutes, catecholamine levels were compared between the 10 infants who developed transient tachypnoea of the newborn (TTN) and 13 controls of a similar gestational age range (31-35 weeks) who developed no respiratory distress in the neonatal period. Infants who developed TTN were more often delivered without labour, 8 of 10 compared to 2 of 13 controls (p less than 0.01). There were no significant differences in adrenaline levels between the two groups. Noradrenaline levels, however, were significantly lower in the infants who developed TTN, being a median of 3.1 nmol/l (range 1.07-5.85 nmol/l) compared to a median of 6.4 nmol/l (range 2.38-22.83) in the controls (p less than 0.01). Infants who were delivered following labour had significantly elevated noradrenaline levels compared those delivered without labour (elective delivery) (p less than 0.05). These results suggest that low noradrenaline levels in preterm infants may explain the association in this group of TTN and "elective" delivery.