This book explores the external audit procedures and techniques applied to complex fair value measurements. Fair value measurements represent a significant challenge for auditors due to their complexity and to their intrinsic subjectivity. International auditing standards provide general guidelines, needing significant effort to be applied to the review of fair values, either under the IAS/IFRS and the US GAAP. This book has a twofold objective. Firstly, it jointly examines key fair value measurements and prescriptions of the international auditing standards. Secondly, it provides an interpretation on how audit standards can be effectively applied to the review of fair value measurements. The first section studies the IFRS 13 focussing on the audit of the different fair value levels and on the audit of the valuation techniques. The second section deals with financial instruments, exploring in-depth the fair value measurements of financial assets and liabilities and their audit review. The third section focuses on the audit of fresh start accounting under the US GAAP. Fresh start accounting is a highly complex task, as it requires to measure all the assets and liabilities at fair value in the fresh start financial statements. The conclusion section emphasizes how external audit is crucial to limit the managerial accounting discretion. At the same time, it underlines that international auditing standards demand further development to codify existing knowledge on the audit of fair value measurements, as well as to provide improved guidance to auditors.