The earning forecast and their revisions have long consumed the attention of investors, managers, financial analysts, researchers and providers of credit. The main source of information for investors, creditors and others active in the stock market is the forecasted earning in the statements issued by the companies themselves. In light of the importance of these disclosed earning per share by the companies , the present paper is an attempt to identify the factors that determine the accuracy of these forecasts , such as size , life of the company , forecast horizon , financial leverage , number of revisions , audit reports , board of the company and the type of industry. The research encompassed 58 companies, in the period 1382 – 1385. The methodology included regression analysis by panel data and repeated measures design. The average error in all observations was 50%, with only 18% of observations indicating a prediction error of less than 10%. The results of the research indicated an inverse relationship between forecast horizon, financial leverage and the life of the company and the accuracy of the forecast. It indicated a relationship between the audit report and the accuracy of the forecast. No other meaningful relationships were identified.