Complex accounting estimates, including fair values, impairments, andvaluation allowances, are increasingly important to financial statements. However, auditors experience significant difficulty inauditing complex estimates, suggesting that audit quality may be low in thisarea. Some of these difficulties can be attributed to highlevels of uncertainty about valuations given volatile financial markets andinnovative securities. However, others arise fromproblems with auditor judgment and the audit process. Analysis of PCAOBinspection reports for the largest accounting firms reveals that fair valuemeasurements, including impairments and other estimates, are amongthe most frequently cited accounts for auditor errors and that, while otheraudit deficiencies have decreased over time, deficiencies involving fairvalues and impairments have not.