The Granger causality test was used to explore the price interdependence in the wholesale tomato markets of Fortaleza, Teresina and Sao Luis in the Northeast of Brazil. Following the results of this study, the conclusion is reached that, in general terms, the prices in these markets are established efficiently implying a competitive environment in the Northeast tomato markets. Fortaleza operates as a leading market "driving" the prices of the Teresina and Sao Luis secondary markets.