A randomized, double-blind study was conducted to assess the influence of 1:200,000 or 1:100,000 epinephrine in a four percent articaine-HCl solution on the concentration-time profiles of epinephrine in the serum of patients during removal of an impacted lower wisdom tooth. In order to estimate the amount of endogenous epinephrine secretion during operation, volunteers were injected without subsequent operation. The heart rate (HR), the concentration of cAMP and norepinephrine were determined as indicators of beta-adrenoceptor stimulation and effective signal transduction. These parameters were correlated with the epinephrine serum concentration. HR measurements were done automatically using the Hewlett Packard monitor, cAMP and the catecholamins were determined immuno- and radioenzymatically. The results showed a dose-dependent absorption of epinephrine from the intraoral depot. The peak concentration and the velocity at which 50% of the epinephrine had been eliminated were affected by the operative manipulation that had induced an increase in endogenous epinephrine secretion. HR, cAMP and norepinephrine were linearly correlated with serum epinephrine.