This paper explores the effect of market access on firms' export performance and their survival in foreign markets. The data used covers all Peruvian exporting firms between 2002 and 2008, a period during which Peru was active in joining the global economy. This is done using two indices, one that summarizes the tariffs faced by exporters, the other that measures the preferential margin at the bilateral level. Results show that more than market access conditions per se, it is market access conditions relative to those faced by competitors that significantly influences export performance and survival. About a fifth of the increase of exports directed to Mercosur countries is due to improvement in preference margins.