several studies show the relationship between audit quality and firm size. most of them confirmed that the large size auditors are positively related with audit quality on the other hand some other surveys have disclose there is no difference between audit firms size in terms of their impact on audit quality both of them have the potential to reach an acceptable level audit quality industry expertise according to literature it is clear that the expertise of the auditor plays an important role in improving audit quality. demanding auditor specialization in an industry leads to a higher level of technical competence and technical information. it is mainly due to auditors potential ability to detect financial statement errors. industry expertise advantages together with general audit knowledge can enhance the audit technical ability and audit reputation and so increase audit quality as well as leading to a higher level of audit fees.