5 volunteers took part in this double-blind, cross-over study to evaluate the role of adrenaline 1:80,000 in lidocaine used in dental local anaesthesia on haemodynamics and the concentrations of catecholamines and their metabolites in plasma. The exogenous adrenaline statistically significantly elevated the heart rate (from 66 +/- 7 to 79 +/- 9 bpm), but did not affect systolic or diastolic blood pressure. Plasma adrenaline concentrations were increased more than 10-fold (from 0.02 +/- 0.02 to 1.0 +/- 0.3 nmol/l). We conclude that the adrenaline present in the local anaesthetic is a major source of adrenergic activation during minor oral surgery.