The European Commission (EC) regulation draft of 2011 contains the
external mandatory auditor rotation (audit firm rotation) as a reform measure to
increase auditor independence. The external auditor firm rotation could Supplement the internal mandatory rotation (auditor rotation) by the 8th EC directive. This article presents an agency theoretical foundation of rotation. In this context, the main influences on low balling and on the expectation gap will be presented. The total effect of the rotation on financial accounting and audit quality is theoretically uncertain, because the rotation can also lead to a decreased independence in a low balling situation and is connected with interrupted or lost learning and knowledge effects by the auditor or the audit firm. Then, a state of the art analysis of empirical research results with regard to auditor and audit firm rotation is focused. In contrast to the assumption of the EC, the majority of the empirical results don’t lead to an increased financial accounting and audit quality by audit firm rotations. Furthermore, the positive effects of the internal rotation period of 7 years and the cooling off period of 2 years by the 8th EC directive are not empirically proved yet.