With a few exceptions, historians have conceded since the work of Labrousse (1932) that grain markets are characterized by a strong seasonality linked to the need for farmers to sell their wheat quickly after harvest. As recent works indicate, the analysis of price movements makes it difficult both to understand the motivations of the stakeholders and to account for the pace of trade. Using statistical methods applied to volumes on 13 markets located in the supply area of the Paris Basin between 1828 and 1852, the analysis of transactions makes it possible to affirm that the phenomena of seasonality are not universal and that they only very imperfectly reflect the functioning of the cereal markets, in particular for maslin, oats and barley, which sometimes represent the bulk of transactions. Seasonality phenomena only concern certain markets, linked to the main trade routes. This study also makes it possible to demonstrate that the modernization of the grain trade in the Paris Basin precedes the establishment of the rail network. It shows too that such modernization is based on the modernization of the local road network and, to a certain extent, on the elimination of traditional markets, particularly for oats. Finally, it makes it possible to propose a typology of markets that takes into account not only the importance of transactions, but their inclusion in regional exchange systems.