In this article, Andrew Bowen examines fraud and auditors' negligence in relation to the ex turpi causa principle. He looks at the case of Moore Stephens v Stone & Rolls Limited which raised the issue of whether a company could rely on the fraud of its sole directing mind and will in an action against its auditors for professional negligence. This article originally appeared in issue 103 of W. Greens Business Law Bulletin and is reproduced here with their kind permission.