present study aims at offering a model to describe the relationship found between aspects of corporate governance factors including ownership structure, dependent and independent directors, and internal audit with gross profit margin of those companies accepted at Tehran stock exchange. The understudy statistical population consisted of 81 companies acting at Tehran stock exchange selected through systematic deletion method. The study was conducted based on financial statements of the understudy companies at a 6-year period during 2004-2009. Multiple linear regression test and T-test were used to test the research hypotheses. The results demonstrated that there is not any relationship between ownership aspects of institutional investors, managerial ownership, and availability of internal auditor and gross profit margin of those companies accepted at stock exchange. Also, there is a reverse and meaningful relationship between foreign ownership aspects, independent directors, free float stocks, and personal ownership and gross profit margin of those companies accepted at stock exchange. While, there is a direct and meaningful relationship between independent directors and gross profit margin of the mentioned companies.
