The purpose of this study was to compare the clinical efficacy of articaine at 4% (epinephrine 1:100,000) with bupivacaine at 0.5% (epinephrine 1:200,000) for surgical extraction of impacted mandibular third molars. Study Design: This was a randomized, double blind, split-mouth, clinical trial. Thirty-six patients took part and underwent extraction of 72 lower third molars. The variables studied were: anesthetic latency time, intra-operative bleeding, anesthetic quality, hemodynamic changes during the surgical intervention, anesthetic duration in the soft tissues, post-operative analgesia and post-operative pain at 2, 6, 12 and 24 hours using a visual analogue scale, as well as any need for additional rescue medication. Results: Latency time was 2.0 minutes for articaine and 3.1 minutes for bupivacaine, with statistically significant difference (p<0.05). Bleeding was greater when bupivacaine was used (p<0.05) and anesthetic quality was greater with articaine (p<0.05). The duration of soft tissue anesthesia was longer with bupivacaine (p<0.05). Differences in post-operative analgesia, haemodynamic changes, post-operative pain and the quantity of rescue medication consumed were not statistically significant (p>0.05). Conclusions: Articaine showed greater clinical efficacy than bupivacaine, reducing latency time, bleeding, anesthe - tic duration in the soft tissues and achieving higher anesthetic quality, requiring less reinforcement during surgery than bupivacaine.