ABSTRACT Inferior alveolar nerve block (IANB) is most commonly used technique performed to anesthetize mandibular tooth. Sometimes it fails even though it’s been performed by well experienced clinicians.The reasons for failure:difficulty in identifying anatomical landmarks, patient compliance, anaesthetic solution,variation in the anatomical landmarks and inflammation.This paper is a review of various studies conducted on failure of inferior alveolar nerve block and Will be discussing in detail about the reasons for failure and how to overcome that. Selecting the best technique by the dentist or surgeon depends on complications related to the alternative techniques.