This study investigates the association between the industry-level auditor competition andaudit quality and audit fees. The audit market has witnessed a continuous decrease of the numberof large audit suppliers (i.e., audit firms). Regulators questioned whether the dominance of theaudit market by a few large auditors reduces the level of competition in the audit market(Government Accountability Office 2003, 2008; European Commission 2010). Specifically, basedon the economic theory on the competition, the regulators expressed a concern that a possiblecollusion among the dominant auditors would lead to a low quality of audit service while chargingoligopolistic high fees. As a result, the regulators asked to academics to investigate the effect ofauditor competition on audit markets. Government Accountability Office (2003, 2008) also lookedinto the issue but did not make any clear conclusion on the effect of auditor concentration onthe audit quality and the audit fee. Following the request, a few recent studies investigate the issue using U.S. data. Thesestudies uniformly use Herfindahl index in each industry at the local audit market to proxy forthe level of concentration in the audit market. To measure the audit quality, they use differentproxies. Specifically, Kallapur et al. (2010) document that Herfindahl index is negativelyrelated to the magnitude of earnings management, suggesting higher audit quality for moreconcentrated audit markets. Similarly, Newton et al. (2013) report that Herfindahl index isnegatively related to the frequency of financial statement restatements. However, surprisingly,Boone et al. (2012) report that firms in the audit market with high Herfindahl index are more likely to meet or beat earnings benchmarks, resulting in lower audit quality. Collectively, thefindings in these studies are mixed at best. In contrast, the studies that examine the associationbetween auditor concentration and audit fees generally reveal that Herfindahl index is negativelyrelated to audit fees, relieving the regulators’ concern that the lack of competition leads tooligopolistic dominance of audit market by a few large auditors who charge high audit fees totheir clients. It seems that the dominance by a few large auditors allows them to enjoy theeconomy of scale, which leads to lower costs in providing audit services. This study uses Korean data and investigates the same issue. In the past two decades, therewere structural changes in the Korean audit market similar to those in the U.S. audit market. However, given the regulatory concerns on this issue and the potential importance of the effectof audit market structure on the audit industry, it is surprising that none of prior studiesinvestigate this issue in Korea. Therefore, this study intends to fill this gap. Our sample consists of listed companies in the Korean stock market with available variablesfrom 1994 to 2012. Empirical findings are summarized as follows. First, we find that industryyearlevel Herfindahl index is positively related to the magnitude of discretionary accruals. This finding shows a sharp contrast to those in the U.S. studies, which document the negativerelation between two variables. This different result suggests an importance of performing Koreanaudit market studies independently from the U.S. studies. Furthermore, we find that thepositive relation between Herfindahl index and audit quality is more pronounced as the Koreanaudit market structure moved from Big 6 to Big 5/Big 4. Second, we find that the Herfindahlindex is negatively related to the level of audit fees. This finding is consistent with those in theU.S. studies. We also find that the negative relation between Herfindahl index and audit feesdid not change significantly as the market structure changed from Big 5 to Big 4. Our findings are subject to some caveats, including whether the Herfindahl index exactlyrepresents the intensity of competition in the audit market. However, our findings are interestingbecause they provide several valuable insights to regulators, academics, investors, and the otherinterested parties. Given that almost no Korean studies investigate the incentives of auditorsrelated to audit market structure, this study provides valuable intuitions. Especially, our findingssuggest that the regulators need to consider weakening the dominant market structure of a fewlarge auditors in order to improve the quality of audit service.