In this study, we have measured the plasma concentration of lignocaine and its metabolite, monoethylglycinxylidin, in 19 premature neonates (gestational age < or = 33 weeks) when lignocaine gel was used for lubrication of an intranasal tube (during continuous positive airway pressure treatment) or an endotracheal tube (for intubation). We did not find any correlation between plasma concentration of lignocaine or monoethylglycinxylidin and weight of the infant (range 795-2530 g). None of the neonates had toxic levels of lignocaine. One neonate had an exceptionally high but not toxic plasma level of monoethylglycinxylidin. However, this neonate had been treated for severe seizures with an iv infusion of lignocaine up to 13 h before the study. In conclusion, we found it safe to use moderate amounts of lignocaine (i.e. 0.3 ml/kg of lignocaine gel 20 mg/ml) for lubricating both intranasal and endotracheal tubes.