The purpose of this study is to investigate how the effects of principles vs. rules based accounting standards and a potential change in the audit reporting model will affect investors' perceptions of management's reporting credibility.  The Securities and Exchange Commission is currently considering the adoption of International Financial Reporting Standards, which is considered to be a set of principles based accounting standards.  Whereas, U.S. Generally Accepted Accounting Principles are considered rules based.  Additionally, the Public Company Accounting Oversight Board is considering a possible change to the existing audit reporting model.  The audit reporting change currently under consideration would require the use of additional emphasis of matter paragraphs within the audit report to discuss areas of higher risk in the financial statements.  A sample of 196 nonprofessional investors completed an on-line 2 X 2 between subjects experiment that manipulated accounting standard type and level of auditor reporting.  Participants assessed direct and indirect measures of reporting credibility, obtained the experimental manipulations, and provided revised credibility assessments.  Changes in credibility served as the dependent variable.  The results suggest that expanded auditor reporting resulted in lower perceptions of management's reporting credibility. Additionally, the effects of expanded auditor reporting appear stronger under rules based accounting standards.  No main effects, however, of accounting standard type were observed.  These results contribute to the existing literature on accounting standard type, the information content of audit reports, and reporting credibility.