There are many factors that could have a potential impact on the growth of a firm. In this research, we examined the relationship between the following economic elements: Size of the firm, Research and development expenditure, Advertisement cost, and the growth of Iranian firms of manufacturing industry. For this purpose, four digit ISIC standard data in manufacturing industry sector have been gathered (based on the published data of the Iran Statistics Center during 1997 to 2007). Then, the effects of the size of the firm, research and development and advertisement on the firm growth were tested. Results showed that research and development and advertisement expenditure factors have positive and significant impacts on the firm growth. In contrast, there was not any significant relation between the initial size of the firm and the growth. Based on the findings of this study, the Gibrat law was confirmed. In addition, the direct relation between the behavioral elements and firm performance was verified. JEL classifications: D92, L25, M37
