The technical Committee of the Audit Organization has issued an exposure draft regarding the analysis of the issues relating to Segmental Reporting. The first issue to resolved by the Committee is whether or not information about segments of an enterprise should be included in financial statements. This article presents the results of a post-test with the control group experiment conducted to determine the effects on investment analysis of the presence of segmental data in financial statements of diversified firms and the results of a cross-sectional survey carried out to determine the costs and benefits of disclosing segmental information in Iran. The authors strongly believe that the benefits of disclosing disaggregated financial information exceed the related disclosure costs and that the introduction of segmental data can significantly reverse ananlysts' evaluations of the diversified firms presented to them in this study. Therefore, they conclude that diversified firms should include segmental data in their annual and interim financial reports.