Audit opinion lends credibility to the company''s financial statements by validating the techniques used for reporting its results. Financial reports assist users to take decisions about the management of the company. The accounts should, therefore, avoid misleading users about the company''s results. The directors'' interest in showing good results about the company''s operations may conflict with the objective of preparing accounts which give a true and fair view. Because of that, it is argued that the need for validation of lack of bias is best provided independently of the source of the information. This book describes the construction of a prototype expert system for forming the audit opinion on a client''s statements. The types of audit opinions in various Auditing Standards were analyzed. Both the knowledge acquisition technique as well as the rule-based representation scheme used for constructing The Expert AOF were described and compared with techniques used to develop similar systems. This book is useful for academics and professionals who are interested in the application of information technology in auditing companies'' financial statements.