Regulators and financial reporting institutions have recently increased their focus on audit committee composition, indicating an acknowledgement of the potential importance of audit committee monitoring efforts on financial reporting quality. I extend prior corporate governance research by exploring whether the duration of service on a specific audit committee (i.e., audit committee tenure) affects earnings quality, future financial performance and cost of capital. Using a sample of 2,355 firm years for fiscal years 1998-2003, I test the potential association between audit committee tenure and GAAP-based earnings quality proxies and find some evidence that audit committee tenure improves earnings quality by limiting the degree to which management relies on accruals to determine income. I also test whether audit committee tenure effectively reduces real earnings management proxies since such techniques reflect routine business decisions that often fall outside of GAAP's jurisdiction. I find that audit committee tenure is associated with the use of abnormally low discretionary expenses, suggesting that current-period earnings are artificially inflated when audit committee tenure is relatively longer. The next stage of my study examines the effect of audit committee tenure on firm performance. Audit committees can influence firm performance by two avenues. First, committee effectiveness can influence the quality of reported earnings, which could reduce the cost of capital and improve firm performance by making positive NPV projects more feasible. The audit committee also oversees risk management activities and internal reporting efforts that are ultimately used by the board of directors to monitor and ratify management's strategic decisions. The results of this analysis provide evidence consistent with the entrenchment hypotheses since audit committee tenure appears to have a negative effect on future firm performance. I conclude the study by analyzing the potential association between audit committee tenure and cost of capital. After employing both cost of equity and cost of debt proxies as dependent variables, I find no significant associations with audit committee tenure.