The financial reports, presented by the companies, lead a role of guiding for a vast number of financial information users (Management, creditors, potential investors, government bodies, labor unions etc.) on their decision-making processes. The independent audit process of this vital function boosts the reliability of financial statements which consists the basis for a decision-making. Materiality in audit is described as; "a fraud, error or misstatement is material when it is at a level where the decisions of the users are effected". The materiality, which poses a vital role in audit processes, is defined by the auditors and has not a generally accepted formula. It depends sometimes on the professional judgement of auditors, on the anatomy of the auditee and on the spesific features of the industry at which the auditee performs. This study, being performed in a conceptual way, has experienced a literature review of both national and global sources on materiality.