Arsenic trioxide is one of the 'tooth pulp devitalizing agents' used through the dental history when anaesthesia was not available. But owing to its capacity to kill cells in surrounding tissues, the use of arsenic trioxide in vital pulpotomy has been reduced. Arsenic trioxide can cause necrosis of gingiva, bone which can cause osteomyelitis of the jaws. But some dentists still continue to use arsenic trioxide in their endodontic practices. The purpose of this article is to present arsenic trioxide induced osteomyelitis on maxilla and treatment process.