本文利用兩期逆選擇與道德危機的模型來探討當公司股東、經理人、會計師之間存有資訊不對稱時，會計師任期與審計品質間之關係。研究結果發現，當經理人有可能虛報盈餘、但股東與會計師之間無資訊不對稱時，任期與審計品質兩者呈正向關係；此種正向關係在股東與會計師之間有逆選擇的問題時則將不復存在，此時審計品質會低於最適水準。此外，會計師會因為道德危機而降低審計品質的情況，只有當同時存在逆選擇問題時才會發生。最後，本研究亦指出，強制性會計師輪調政策並無法提昇審計品質。

This paper examines the relation between audit tenure and audit quality in the presence of information asymmetry among the stockholder, the manager, and the auditor. Using a two-period adverse selection and moral hazard model, we show that even when managers are inclined to overstate earnings, auditor tenure is positively associated with audit quality as long as no asymmetric information exists between the auditor and the stockholder. However, when an auditor has hidden information about his/her efficiency, this positive association disappears and audit quality is lower than the socially optimal level. Moreover, moral hazard will lead to a suboptimal audit quality only when the problem of adverse selection exists at the same time. Finally, our result suggests that mandatory rotation is not a cure for improving audit quality.