To improve audit effectiveness, public accounting firms have organized their practices to include hierarchical review by teams organized along industry lines. We examine how industry specialized auditor teams detect errors, using a sophisticated experimental design. Our analysis of nominal teams created from seniors and managers working individually shows that seniors add value to the team by detecting more mechanical errors while managers detect more conceptual errors. Working within specialization, managers and seniors both contribute in a nonredundant way to the team’s overall effectiveness. We also find that the nominal teams outperform real teams in the detection of mechanical but not conceptual errors. These results only hold when the auditors work within in their industry specialization. Out of specialization the auditors are not effective at detecting errors, and real teams perform below the nominal team benchmark in the detection of both mechanical and conceptual errors.