14 pages, Price dispersion across markets is common in developing countries. Using novel market and trader-level data, this paper provides estimates of the impact of mobile phones on price dispersion across grain markets in Niger. The introduction of mobile phone service between 2001 and 2006 explains a 10 to 16 percent reduction in grain price dispersion. The effect is stronger for market pairs with higher transport costs. (JEL O13, O33, Q11, Q13)