To evaluate success of pulpal anaesthesia of mandibular 1st molar by using 4% articaine in buccal infiltration versus 2% lidocaine in inferior alveolar nerve block. Randomized control trial. Department of Operative Dentistry, Sardar Begum Dental College, Gandhara University, Peshawar, from March to August 2014. One hundred and fifty-six emergency patients, who had 1st molar diagnosed with irreversible pulpitis, participated in the study. Subjects were divided into two groups by random allocation. One group received 4% articaine buccal infiltration and the other group received inferior alveolar nerve block of 2% lidocaine. Subjects’self-reported pain response was recorded on Heft Parker Visual Analogue Scale after local anaesthetic administration during access cavity preparation and pulp extirpation. Mean age of subjects was 31.46 ±10.994 years. The success rate of 4% buccal infiltration was 76.9%; whereas the success rate of 2% lidocaine inferior alveolar nerve block was 62.8%. There was no statistically significant difference between the two groups. 4% articaine buccal infiltration can be considered a viable alternative to 2% lidocaine inferior alveolar nerve block in securing successful pulpal anaesthesia for endodontic therapy.