Information asymmetry of market brings undesired outcomes such as little participation of investors, high trade costs, weak markets, and low trade profits. Regarding to the importance of information asymmetry concept, the goal of this research is study of relationship between Corporative ownership and information asymmetry in companies accepted in Tehran Stock Exchange. A sample of 97 companies, members of Tehran Stock Exchange, was selected for a 5 year period (2007-2011). Linear regression model with confidence level of 95% and software Excel and SPSS were used to test the research assumption. The results show that there a reverse (negative) relationship between Corporative ownership level with information asymmetry.