To assess the effect of epinephrine-containing local anesthetics on vasoconstriction, we immunohistochemically measured the intravascular lumen area in different regions of the mandible. Twelve male Wistar rats were used. General anesthesia was induced and maintained with sevoflurane. Infiltration anesthesia was performed with 0.2 mL of epinephrine-free 2% lidocaine (E−) near the left mandibular first molar and with 0.2 mL of epinephrine-containing 2% lidocaine (E+) near the right mandibular first molar. After decalcification, the specimens were paraffinized, and thin sections were prepared and immunohistologically stained with an antismooth muscle actin antibody. The intravascular lumen area was measured in the mucosa, periodontal membrane, Haversian/Volkmann's canal, and bone marrow. A Mann-Whitney U test was used for statistical processing, and p < .05 was considered to indicate a statistically significant difference. In the oral mucosa and the periodontal membrane, E+ had a significantly smaller vascular lumen area than E−. In the Haversian/Volkmann's canal and the bone marrow, no significant intergroup difference was observed in the intravascular lumen area. We postulate that this is due to a low smooth muscle content of blood vessels in the mandible and suggest that the vasoconstrictive effect of epinephrine-containing local anesthetics within the mandible is ineffective.