Â Â Â Â Â Â Â Â Â Â Abstract Â Based on the recent literature of heterogeneous firms, productive firms self select themselves into foreign markets. In this framework, there is a productivity rise prior to exporting. On the other words, different export performance across firms is linked to their heterogeneity. Â The main purpose of the present paper is to examine the so-called hypothesis of heterogeneous firm in Iran. For this, we have used the last Iranian manufacturing industries data at 4 digit aggregation of ISIC classification during 2000-2010 and examined the hypothesis by using generalized method of moments. The obtained results show that productivity has a relationship with export in both short and long run. So, productivity enhances the competitiveness of the firms in international markets and then firms with high productivity enter global market and consequently export increases. Based on the results, the hypothesis is verified. Regarding to the importance of export in economic development, we suggest that it should be paid more attention to productivity in industrial development policies. Â Â Â Â Â Â JEL Classification: F12, L1.