Introduction: This study compared the efficacy of two anesthetic solutions for inferior alveolar nerve block in patients with irreversible pulpitis. Material and methods: This prospective, randomized, double blind study included 66 subjects. The subjects were randomly divided into two groups of 33 and received conventional inferior alveolar nerve block as follows: Group A- 2 cartridges of 4% articaine with 1:100000 epinephrine and Group B – 2 cartridges of 2% mepivicaine with 1:100000 epinephrine. Access was begun 15 minutes after inferior alveolar nerve block, and subjects were instructed to report pain felt during access and mechanical preparation. The success rate of inferior alveolar nerve block was defined as access and instrumentation of root canals with no pain or mild pai. If subject felt any pain, this was considered failure. Subjects needed supplemental anesthesia was recorded. Results: There was no significant difference in the efficacy of inferior alveolar nerve block between mepivicaine (45.5%) and articaine (48.5%) groups. Conclusion: None of the anesthetic solutions had an acceptable success rate for inferior alveolar nerve block in patients with irreversible pulpitis and both grops were similar regarding the need for supplemental anesthesia