Explaining and the determinants of dividend policy is one of the biggest challenges that have long been the center of attention of accounting and financial researcher and theoreticians. There are many evidences that confirm the effects of dividend and there are a lot of other potential factors whose effects on the dividend policy have not been studied yet. In this study, the effects of four variables including asymmetric information, growth opportunities, cash holding and firm size in payout dividend policy are investigated, simultaneously. The study uses the information of 140 companies listed on Tehran Stock Exchange over the period 2005-2010. In this study, 4 hypotheses are proposed and investigated. There are positive and significant relationships between asymmetric information, growth opportunities, cash holding and company size on one side and payout dividend policy on the other side.