some researches made in the field of agency problem issue, deal with the role of control systems regarding owners and managers. in this research the relationship between the two control mechanisms, namely the voluntary disclosure (external control mechanism) and outside directors (internal control mechanism), which are reductive of agency problems, has been studied. for this reason, a sample consisting of 239 manufacturing companies listed in tehran stock exchange (tse) which have published financial statements and management discussion and analysis report for 20 march 2007 was taken. voluntary disclosure has been identified by 71 revised indexes applied in previous studies. results show that, the applied model describes 20 percent of changes in the voluntary disclosure that is as about the previous findings. however, there was no significant relationship between voluntary disclosure and outside directors. this study is a movement towards the future researches regarding the voluntary disclosure, and emphasizes the transparency in capital markets.