This study attempts to understand the organizational drivers of internal audit effectiveness in the light of recent changes in the 'mission' of internal auditing and its central role in corporate governance. On the basis of data from 153 Italian companies, our survey shows that the effectiveness of internal auditing is influenced by: (1) the characteristics of the internal audit team, (2) the audit processes and activities, and (3) the organizational links. Internal audit effectiveness increases in particular when the ratio between the number of internal auditors and employees grows, the Chief Audit Executive is affiliated to the Institute of Internal Auditors, the company adopts control risk self-assessment techniques, and the audit committee is involved in the activities of the internal auditors.