SYNOPSIS Auditing Standard No. 5 (AS5) introduced by the Public Company Accounting Oversight Board (PCAOB) in June 2007 requires a top-down risk-based approach in auditing and is expected to improve audit efficiency and make the overall auditing process timelier by reducing audit report lags. We investigate the impact of AS5 on audit report lags over an extended period from 2006 to 2011 and find that audit report lags are lower in the AS5 years (2007–2011) relative to the AS2 years (2006–2007). But this reduction is evident mostly for the firms with clean SOX 404 opinions. The presence of material internal control weaknesses (ICW) significantly increases audit report lags, but AS5 does not have any incremental moderating effect on report lags and the ICW relationship. Tests for the firms with company-level and account-specific ICWs demonstrate identical results. Additional analyses show that the learning curve effect takes place rapidly in the early part of the AS5 period and audits continue to remain efficient in terms of reduced report lags in the latter part of the AS5 period relative to the AS2 period. The year-to-year change analyses for the AS5 period further corroborate this result. Overall, our study demonstrates that the top-down, risk-based approach under AS5 makes the audit process more efficient and timelier by decreasing audit report lags. Data Availability: Data are available from public sources identified in the paper.