This study proposes auditors' effectiveness in the transmission (AET) of GAAP misstatements as a new measure of audit quality that is obtained from the audit report. We carry out a content analysis of the audit reports of a sample of 533 pre-bankrupt Spanish firms and find that the poorly enforced Spanish environment results in strategies of a lower than expected effectiveness in three aspects: the type of qualification chosen, the wording used and the adjustments proposed. We subsequently use AET to test for audit quality differences in three dimensions: auditor size, audit market experience and the client's closeness to failure. Larger auditors are more effective in the transmission of the GAAP misstatements. We also find increasing audit quality throughout our 1990-2001 period of analysis and with the clients' closeness to failure. Our results constitute a reference for regulators, not only in Spain, but also in similar European code-law regimes where qualifications for GAAP violations are usually included in the audit reports.