The local and systemic effects of epinephrine and acetylcholine on tooth pulp pressure were evaluated in dogs by intra-arterial and intravenous injection of these compounds. Control pulp pressure recorded from the dog's canine tooth was 58 +/- 6 mm Hg. Intra-arterial epinephrine produced dose-related decreases in pulp pressure which were antagonized by alpha-adrenergic receptor blockade with phentolamine. These results suggest that the fall in pulp pressure is the result of local vasoconstriction and reduced blood flow into the pulp. Acetylcholine did not affect pulp pressure, suggesting a lack of cholinergic vasodilator receptors in the pulp. The intravenous epinephrine and acetylcholine resulted in alterations in pulp pressure in the same direction as systemic blood pressure changes. This study indicates that pulp pressure is affected by systemic blood pressure changes as well as by local sympathetic nervous system effects.