Although longstanding arguments suggest that the need to acquire information contributes to spatial concentration of employment, few studies have provided evidence on this point. This paper addresses this issue by examining the spatial concentration of headquarter activity of exporters. Exporting requires specialized knowledge of foreign markets and should, therefore, contribute to spatial concentration. We test this idea by applying differencing methods to 4-digit industry-level data for the fourth quarter of 2000. Results suggest that when foreign market information is difficult to obtain, exporter headquarter activity is more agglomerated. Results also indicate that the sensitivity of agglomeration to foreign trading environments depends on the underlying characteristics that define countries as ''difficult.''