The main etiological factor in the pathogenesis and progression of pulpal and periradicular diseases is microorganisms especially bacteria. The main objective of root canal treatment is to create an environment in which remaining microorganisms cannot survive. This goal can be fulfilled by use of supplemental antibiotic therapy in conjunction with regular non-surgical root canal treatment. In endodontics both systemic and local antibiotics are broadly used. In endodontic infections the local administration of antibiotics are more efficient when compared to systemic administration. In a nutshell this article elaborates the use of antibiotics in endodontics.